The self check in terminals are fine, but fat lot of good it does when i still have to stand in a huge line just to have the human behind the desk put a sticker on my checked baggage. WTF is that about? ... Why can't the terminal simply spit out my baggage sticker for myself to put on?
It may be about putting the sticker on correctly. If the sticker isn't put on correctly (positioned so automated scanners can read the bar codes and securely attached so it won't fall off), the bag may not make it to the destination in a timely fashion. Granted that putting on the sticker isn't hard, but some people have difficulty with seeming simple things. In addition, having an airline employee attach the sticker before the luggage is accepted allows for a human check to ensure things like: the bag is within dimensional limits, the bag isn't already damaged, the bag is in fact "approved" luggage that is sturdy enough to withstand air travel, etc.