Presumably because after people wanting them to do somehting about diving and cheating they bought the rule in, banned 2 players but realised they'd made a complete arse of it so quietly dropped it unless there is an incident which is the most obvious blatant 100% nailed on dive to win a pen, then they'd maybe bring it back for that, otherwise they won't bother.
Certainly suggests there isn't a bias for "the big 6" when 18 other clubs haven't suffered from it either, cause i'm pretty sure they didn't manage to eradicate all cases of simulation.