Why is the hand cut off in the case of stealing but not in the case of (daylight) robbery or seizing by force?
Question

                What is the difference between the thief (saariq, one who breaks in by stealth and steals something that is kept in an appropriate place) and the robber (muntahib, one who takes something by force in front of others)? Why is the hand cut off in the first case and not in the second?
Praise be to Allah. 
          Ibn al-Qayyim said: 
 
          The fact that the hand of the thief (saariq) may 
          be cut off for three dirhams, and not in the case of the opportunist 
          thief (mukhtalis, one who steals when a person is not looking), 
          robber or extortioner (ghaasib, one who seizes something by force) 
          is indicative of the perfect wisdom of sharee’ah. For one cannot take 
          precautions against the thief who breaks into houses and breaches one’s 
          hiding-places and breaks locks; the owner of the goods cannot do any 
          more than that (i.e., hiding them in appropriate places). If it were 
          not prescribed for the hand of the thief to be cut off, then people 
          would steal from one another in this manner and a great deal of harm 
          would be done, and the problem of theft would be grievous indeed. This 
          is unlike the case of the robber and opportunist thief, for the robber 
          is the one who takes things openly in the sight of people, so they may 
          stop him and restore the rights of the one who has been wronged, or 
          they may testify before the judge. And the opportunist thief is the 
          one who takes things when the owner is not paying attention, etc., so 
          there has to be some form of negligence which enables the opportunist 
          to steal, otherwise when one is careful and alert, he cannot take anything. 
          So he is not like a thief (saariq), rather he is more like a 
          betrayer.  
 
          Moreover, the opportunist theif (mukhtalis) does 
          not take things from a place where things of that nature are usually 
          hidden, rather he waits until you are not paying attention, then he 
          takes your things when you put something down for a moment and are not 
          paying attention. This is something against which precautions may be 
          taken in most cases, and he (the opportunist) is like the robber who 
          steals openly. With regard to the one who seizes things by force, the 
          case is more obvious: it is even more apt that his hand should not be 
          cut off, but it is permissible to put a stop to the actions of these 
          people by beating them, making an example out of them as a warning to 
          others, imprisoning them for lengthy periods and punishing them by seizing 
          their property.