What else would make people pay a fee? I do not think alturism would pay for an infrastructure of 300 mio USD and increasing.
What else, is that the miners don't mine if it's not profitable. And it's NOT altruism to pay a fee to the miners. You can't use bitcoin without miners, so if you want to use bitcoin, you pay a fee. If you DON'T want to use bitcoin, then surely the question of whether or not you WOULD choose to pay a fee is irrelevant?
There are TWO incentives to pay fees - getting your transaction in a block, and having a bitcoin currency at all. Increasing the blocksize may attenuate the first incentive but doesn't remove the second at all.