>>55649402Sleep is only banned in certain metas. It will be unbanned in Gen 10. It's just Gen 5 and Gen 9 where it's banned because metas where 1 turn leads to you losing the whole game cannot afford to let sleep run around.
It's why Darkrai, a Pokemon heading for UU here shortly, was considered an S-tier threat in Gen 4/5/6 Ubers. When Smeargle got Dark Void nerfed into oblivion, Darkrai ceased to be a serious Pokemon in Ubers. That's because the main thing Darkrai provided that made it so strong was sleep. Ubers was and is so powerful that a singular bad turn can lead to a game over. Gen 9 OU has reached that threshold.
I do think it should've been suspect tested, however. It probably still would've gotten banned but it would've been a much easier pill to swallow than having the council dictate it.