restriction wise it would be the same reason we have tomes, we eventually do away with tomes, it's just a stopping power eventually we get rid of old restrictions that would do more hindering than help.
i will say atm a lvling potion isn't what is needed it's just the 2.1-2.55 questline to be made optional that is the only real sluggish part of the whole lvling process atm as you have to do it to get to heavensward.