I think thats a pretty simple answer; when was the last time you interacted with a 4th dimensional object be it representation or not? For the most part I think people base their perception of reality on their experience and so if you have never interacted with something, how could you imagin it?

Reminds me of this youtube video I saw some time ago of someone that posed the question of what would minecraft be like if it was in non-euclidean space. The author said it took some time to get used to it and when they tried to play normal minecraft it gave them motion sickness.

If you have no knowledge of what a car is or its internals are like, could you still imagin what's inside?