Sleep Clause was first introduced by Pokemon Stadium, as well as other causes. Some we made ourselves, like Evasion Clause. Technically, it is changing the mechanics, but its more a ban then modifiying the mechanics to change how things work e.g. making SR a two-turn layer. It's like us banning Garchomp from the metagme, whilst in normal pokemon mechanics, it's allowed in pokemon battle tower.
I still like Spikes, as it normally hits most of an opponent's team, and Skarmory and Forry are certainly usable. Tspikes though has issues, being made useless by Tentacruel, and not effecting some of the many overused OUs like Scizor and Heatran.