>>715500904Pokemon battles have no real drawback to switching.
Theoretically everytime the opponent uses a super effective move, there's nothing stopping you from switching to a pokemon that resists it, then using a healing move as the opponent then switches themselves to something that beats what you switched to.
There's a lot more nuance to that, but that's the gist of it.
Stage hazards give you chip damage on the opponent every time they switch.
So not only are they not able to switch forever, it also incentives them to switch less.