should kids be allowed to draw on walls?

No, According to me kids should be allowed not to draw on walls. They can be made to express their artistic side on the paper or in colouring and painting books and scrapbooks.
When kids draw , the have a tendency to express themselves everywhere they feel like. They should be made to stop , so that they dont continue to scribble on other times and then further on furnitures and finally on walls.
When kids draw on walls , this keeps damaging the wall, not always do.we have editable and washable walls. So keeping in mind the cost of re-painting the walls it would be smart to train our kids to continue to paint and scribble on walls .
It is dangerous to keep letting kids draw on walls and every random thing or furniture at our house , because this might or will become an habit which will lead the kid to destroy public property and draw graffiti on public walls and be arrested on charges of vandalism.
Art should not be restricted, yes it shouldnt be but it should be directed to the perfect place and thing. We should encourage our kids to join art classes if they seem to be over enthusiastic about the mix of colours and in drawing.
We should buy them enough colouring books and proper quality colors and kit so that they can be still washed off our walls if they scribble on it. The colouring books should be interesting and appealing enough for the kid to keep him restricted in the book. They should be given large sized drawing books so that their canvas is big enough to express themselves to the fullest extent.

According to me the kids are not allowed to draw on the walls because if they draw by sketch pains than it harms the pant of the wall and it also not look good. If they force you that they want to draw than on such case you can give them chalk to draw. which can easily erase and not harm the paint.