Now that airlines charge for checked bags on domestic flights, an increasing number of people (including me) bring a carry-on and a personal item (i.e. a full-sized backpack) instead of checking any bags. But, because there typically isn't enough room in the overhead bins, airlines preemptively offer to gate check bags to speed up the boarding process. So, in effect, you get one free checked bag if you're willing to carry it through security.
Some airlines send gate checked bags to the baggage claim like any other checked bag, but others make you wait at the gate to pick them up. While I understand that they want to discourage people from abusing gate checked bags, having droves of people crowd the gangway as people are trying to deplane seems inefficient. They should just send the bags to the baggage claim.