Further questions on engineer class

I seem to have come up with further questions to ask:
Is quickfoot suppose to increase the speed when your in the vehicle?
Or should the engineers be the only ones to be abe to move faster in vehicles?
As I have seen, quickfoot does not affect vehicles, is there a reason for this or is it that this topic has never come up yet?
Or should all classes after purchasing quickfoot be able to move faster in vehicles also?

Also we all know stunt vehicles increases the height of the amount of jump you can do in your vehicles, but does powerjump increase it more or should it, or is it irrelevant?