Smogon strays away from complex bans, and looks at the whole Pokemon when deciding to ban something. Banning part of a Pokemon only happens on rare occasions, and when it happens, it applies to all Pokemon, not just the one mon (for example, Arena Trap).Is Blaziken Uber even if he doesn't have Speed Boost? I wanted to use him on an OU team with Blaze, but he was still banned. I thought sometimes pokemon are re-tiered if they do not use the ability that made them broken in the first place.
Because Speed Boost isn't banned on all Pokemon, and because it would be absurd to ban Speed Boost just to make Blaziken not broken, Blaziken remains banned.