The reason why the husband is regarded as superior and is given the role of qawwaam (protector and maintainer)
Question

I am a Muslim girl, praise be to Allah. I have read a lot and I have heard the scholars speak about the husband’s rights over his wife, and how great he is. I have heard ahaadeeth which speak sternly about a woman disobeying her husband. I want to obey the commands of Allah and His Messenger when I get married, if Allah wills, but I have a question, if I may ask about it. This question is going around in the minds of many women, but they are too embarrassed to ask them lest they be accused of ignorance or of denying the command of Allah and His Messenger. The question is: what is it that makes the man superior so that he deserves all these rights over women?.
Praise be to Allah.The great rights that a husband has over his wife are something that is affirmed in sharee’ah, as Allah says (interpretation of the meaning): 
“And they (women) have rights (over their husbands as regards living expenses) similar (to those of their husbands) over them (as regards obedience and respect) to what is reasonable, but men have a degree (of responsibility) over them. And Allah is All-Mighty, All-Wise” [al-Baqarah 2:228] 
“Men are the protectors and maintainers of women, because Allah has made one of them to excel the other, and because they spend (to support them) from their means. Therefore the righteous women are devoutly obedient (to Allah and to their husbands), and guard in the husband’s absence what Allah orders them to guard (e.g. their chastity and their husband’s property). As to those women on whose part you see ill-conduct, admonish them (first), (next) refuse to share their beds, (and last) beat them (lightly, if it is useful); but if they return to obedience, seek not against them means (of annoyance). Surely, Allah is Ever Most High, Most Great” [al-Nisa’ 4:34] 
And the Prophet (peace and blessings of Allah be upon him) said: “If I were to command anyone to prostrate to anyone other than Allah, I would have commanded women to prostrate to their husbands. By the One in Whose hand is the soul of Muhammad, no woman can fulfil her duty towards Allah until she fulfils her duty towards her husband. If he asks her (for intimacy) even if she is on her camel saddle, she should not refuse.”
Narrated by Ibn Maajah, 1853; classed as saheeh by al-Albaani in Saheeh Ibn Maajah.  
And there are other similar texts. 
Allah has explained the reason in the verse where He says (interpretation of the meaning): 
“because Allah has made one of them to excel the other, and because they spend (to support them) from their means” [al-Nisa’ 4:34]
This superiority is something that Allah has decreed, and He is not to be questioned about what He does, rather they are to be questioned. It is also because of what the man does, spending on his family and striving to earn a living for them. 
Ibn Katheer (may Allah have mercy on him) said in his Tafseer (1/363):  “The phrase ‘but men have a degree (of responsibility) over them’ means that they are superior in physical nature, attitude, status, obedience to the commands of Allah, spending, taking care of interests, and virtue, in this world and in the Hereafter, as Allah says (interpretation of the meaning): 
‘Men are the protectors and maintainers of women, because Allah has made one of them to excel the other, and because they spend (to support them) from their means’ [al-Nisa’4:34].” End quote. 
He also said (1/653): “Allah says (interpretation of the meaning): ‘Men are the protectors and maintainers of women’ meaning that men are in charge of women, i.e., they are their leaders, who rule over them and discipline them if they go astray. ‘because Allah has made one of them to excel the other’ means, because men are superior to women, and men are better than women. Hence Prophethood was given to men only, as is the highest position of authority (i.e., khilaafah or the position of caliph), because the Prophet (peace and blessings of Allah be upon him) said: “No people will ever succeed who appoint a woman as their ruler.” Narrated by al-Bukhaari from the hadeeth of ‘Abd al-Rahmaan ibn Abi Bakr from his father. The same applies to the position of judge etc. ‘and because they spend (to support them) from their means’ means, because of the mahr, spending and maintenance that Allah has enjoined upon men with regard to women in His Book and in the Sunnah of His Prophet (peace and blessings of Allah be upon him). So men are better than women in and of themselves, and they have the responsibility to spend on them and maintain them, so it is appropriate that the man should be the protector and maintainer of the woman, as Allah says (interpretation of the meaning): ‘but men have a degree (of responsibility) over them’, i.e., they are in charge of them. She should obey him in that which he commands her to do, and obeying him means treating his family well and protecting his wealth.” End quote. 
Al-Baghawi said in his Tafseer (2/206):  “ ‘because Allah has made one of them to excel the other’ means, men excel women because they have more powers of reason and religious commitment and they are in charge of affairs. And it was said that this refers to giving testimony, because Allah says (interpretation of the meaning): ‘And if there are not two men (available), then a man and two women’ [al-Baqarah 2:282].  And it was said that it refers to jihad, or to worship i.e., Jumu’ah and prayers in congregation, or that it refers to the fact that a man may marry four wives, but a woman is not permitted more than one husband; or the fact that divorce is in the man’s hand; or that it refers to inheritance, or to diyah (blood money), or to Prophethood.” 
Al-Baydaawi said in his Tafseer (2/184): “ ‘Men are the protectors and maintainers of women’ means that they are in charge of them and take care of them. He gave two reasons for that, one that is inherent in them and one that is acquired subsequently, and said: ‘because Allah has made one of them to excel the other’, because Allah has favoured men over women by making men more perfect in reasoning and running affairs, and has given them more strength with regard to work and acts of worship. Hence men are singled out when it comes to Prophethood, leadership, guardianship, establishing rituals, giving testimony in legal matters, the obligation to engage in jihad and pray Jumu’ah, and so on, and they are given a greater share of inheritance, and divorce is in the man’s hand. ‘and because they spend (to support them) from their means’ refers to what they spend with regard to marriage, such as the mahr and maintenance, etc.” End quote. 
In conclusion, men have been given the role of protectors and maintainers for the two reasons mentioned in the verse, one of which is inherent i.e., Allah has made men superior to women, and the other of which is acquired by the man through his own hard work, which his spending his wealth on his wife. 
And Allah knows best.