I think they would be less apparent

I have to agree with you on that.

But regarding kids seeing things, they tend to be constantly imagining new stuff which is actually good for them, that is why they play so much with their toys, it helps them develop their brain.

But once we are adults, constantly seeing faces that aren't there is quite the problem.

that we are not allowed in modern Western world

Not sure if they are not allowed, but clearly they are not promoted, that is a fact indeed.