I guess that's just how F2P goes in games where most content is P2P.
GW2 has actually had remarkably little powercreep compared to other games, but even so, there's still enough that players without a glider, mounts, elite specs, etc will struggle to keep up.
I wish there was a way for players to reduce their own power in OW in exchange for slightly increased rewards, even if those rewards were account bound. Most players would go for this (I think) and it would reduce how much stuff gets obliterated in seconds without making players feel like they got nerfed.
My guess is legally protecting themselves against potential new laws and regulations, so they have more time to make changes or continue making money if these practices get outlawed.
It's not; it exists in computer and console gaming too, just to a lesser extent. As to why, my guess here is that mobile has a lower barrier to entry, and they're always accessible where a computer or console might not be. There's probably some sort of "cultural" aspect here too, where it's already prevalent in mobile so people are more accepting of it, but computer/console gamers had their own culture where this didn't exist for many decades and so won't be as accepting.