There is just no reason for it.

We were at our doctor's office the other day and this sign was on the door of the room where we were waiting for the doctor:



A couple comments/questions to the authors of the sign:

1.  Thank you for specifying "child/children."  If you had said only child, and I had two children, I would have assumed that I could have allowed one child to put stickers on things, but not the other.  Also, if you had just said children I would have been confused if I only had one child.
2. You are very specific about where I cannot allow my child/children to place stickers.  I assume that your specificity combined with a lack of an "etc." means that I can allow my child/children to put stickers on non-listed items, such as the sink, bed, magazines, etc.?
3. How many "sticker incidents" had to have happened before you decided that this sign was necessary?
4. Finally, before you put up a weird sign telling parents what they should probably already know, you might consider either not giving out stickers, or handing them to the child/children as they are walking out the door.