But maybe it will discourage people from taking so much on the plane. The amount I've seen some people take on as carry on makes me dread how much they had as check in.
If anything, the baggage fees encourage people to try to get away with taking too much on board as carry-on. Not that I want to see airlines gouge their customers further, but I sometimes wish they'd charge for carry-on as well just to discourage passengers from trying to take everything but the kitchen sink aboard as carry-on.
I usually fly first class so I don't incur baggage fees, but I don't care for the practice. They should spell out the exact price of a ticket instead of inflating the price afterwards with all of those added fees.