The number of users hasn't really gone up since 3G. By that point in the US basically everyone had a cell phone. So your point is more like increased data usage across the board. And sure that's a decent argument why carriers want to deprecate old protocols, although I think carriers being allowed to deprecate what was effectively a single generation old was a travesty.
I'm just saying as far as service level and amount of data on plans, I personally was content with 3G levels. There's so much advertising pushing us into churning for technolust incrementalist spec-chasing, that I find completely uncompelling as what really defines my devices' capabilities is software freedom.