Because it’s still a bad idea.
The confusion isn’t even really the worst part of moves like Petal Dance, because you can always just switch out. The trouble is being locked into those moves, and unable to switch out, while they continue. Dragon-types can get away with using Outrage because so few Pokémon resist Dragon attacks, and even then it’s kind of a gamble. If you’re using Petal Dance, your opponent basically has a free switch to any of the seven elements that resist Grass attacks (and if Petal Dance keeps going for a third turn and gives the switch-in a chance to set up, you might really be in trouble).
I mean, it’s not useless, but it’s not really good enough that it becomes a better option than Chlorophyll.
Pokémaniacal 