>>45722392From a tournament perspective, because there's no real unfair advantage to it and it isn't detectable unless you fuck up with illegal balls or outright admit to it. Getting a perfect battle ready Pokemon can take as little as 10 minutes now so the argument of having to spend all day breeding to get a team falls flat even though it would have held up a few years ago.
Genned Pokemon still have to stay in the realm of what's possible in-game so you can't just show up with everything having 999 in every stat.
Using an aimbot gives you an actual, unfair advantage over people who aren't using one though, while someone using a genned Pokemon wouldn't have any real advantage over someone who was using that exact same set except they bred theirs.