Why are oxidation states such a fundamental quantity for elements?


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> Why is it that there are fixed oxidation states for most elements out there, with no to very rare exceptions? 
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I was taught that oxidation state is a totally artificial concept we have invented for book-keeping purposes. How is it that its applicable so widely? I understand the case of formal charges, because that is what keep into consideration when making bonds in the first place.


But oxidation state is somewhat arbitrary, because we don't think about electronegativity when we are making bonds. So can someone help me understand the intuitive reason behind it, its been bothering me for months now?


