Thank you for the clarification :)Well generally we want to avoid complex bans unless the impact on the meta by doing a simple ban would be too far reaching (hence drizzle + Swift Swim being a thing). Banning certain abilities on certain Pokemon is complicated both technically and ideologically, so generally we try to avoid them whenever possible. As for just banning the ability itself, that isn't really fair to all the users of the ability that AREN'T broken with it. Pokemon like Ninjask, Yanmega and Sharpedo aren't even remotely broken with Speed Boost, so banning the ability alone would have a lot of collateral damage.