The seats are assigned. People have been standing in line for 15 minutes now. Why on earth would anyone want to stand there, when they could just sit and wait until the line clears?
I understand wanting to get off a plane ASAP, but boarding? You just end up sitting on the plane, waiting for everyone else to get on.
I don't know about saving money, but around here airlines have been creeping up checked bag fees for years. You used to get one free checked bag but when they started charging for all checked bags people started trying to fit thier entire vacation worth of stuff into carry-on. The bags I see people trying to fit into the overhead now are huge and just barely fit in the compartment on smaller planes.
The airlines know what's up though since they'll charge for checked bags but then announce repeatedly before the flight that they're looking for volunteers to check their carry-on to its final destination for free. I actually saw one airline enforce the carry-on sizing device as people were boarding and forced any oversize bags to be checked. A lot of unhappy people that day.
I've really never minded gate-checking, and when I travel alone (i.e. for work), I travel light and try to cram everything into a larger carryon and gate check it.
The biggest bottleneck on the way out is waiting at baggage claim. Gate checked bags are returned to you at the tarmac or at the end of the PBB, and sometimes they are there waiting for you before you even get to it, making it the quickest way out of the airport.