While I've enjoyed levelling jobs on my alt with the road buff, sprouts on a road world might level faster than they learn their game, imo. Especially, if they do not have prior mmo-experience. You drown in tutorial popups and so many different menues and old systems - while you level super fast. This is so much easier when you know the ropes, because you have seen it all, have unlocked everything (maybe on another character), know where to get what.
Of course there will be people who enjoy switching from one job to another and levelling 4 with the msq, others might just want to stick to one job and one role for their start.

Having things to unlock faster might even add to the confusion some have, because they are hard pressed to choose what to unlock and what to postpone. Honestly, the sheer amount of blue quests is daunting to new players. There are videos around for this sorting through all of them to pick out the more important ones and those vids targeted sprouts levelling without that buff.

Right now if you are on a road-server, you either outlevel everything and forgoe the msq-xp or you spread it out to different jobs. Those are your options. So, I for one, completely understand the OPs wish to be able to turn the buff off. The only other option I see for you @ Miravlix would be to start fresh on a server without that prefered status, so you'd have a slower pacing.