Because they’re aiming at a different market, where mobile games are aimed at casuals, while PC/console is for the traditional/hardcore gamers.
Casual gamers have a very different habit compared to traditional/hardcore ones, where they prefer playing free games, instead of the ones who requires payment in-front, but they won’t hesitate to spend hundreds of dollars if they’re liking the game.
This is pretty much the exact opposite of traditional/hardcore gamers, where they prefer buying games, and not too fond of free-to-play ones, due to the overwhelming micro-transactions, and sometimes pay-to-win nature.
Now, could the mobile game devs create games with PC/console quality? Of course they can, and there’s already some examples of it, like Call of Duty Mobile, League of Legends: Wild Rift, or Genshin Impact.
But they won’t abandon the free-to-play model, because they know that putting up a price tag on those games will greatly affects the revenue and users, since in the end, they’re still aiming for the casuals, which will bring much more money compared to the traditional/hardcore gamers