Not removing it from blu does in turn mean that the pyro has to give up his secondary, mostly a hitscan weapon such as the shotgun.
Altough there are these spicy new flamethrower physics, that would make him useless in situations where reds and rebellers are stacked, and how often do you need the crowd control? Keeping the Thruster would only encourace its usage and lead to even more problems on the Jailbreak server.
However you put it, it keeps being useless for blus as with the crits, even as pyro, you barely have to do long hunts over levitation, wich then again, would counteract that tought as you will give up range with using the thruster instead of the shotgun.