Yuuup. Gum is not allowed, because people stick gum in places etc. Therefore banned. Because lots of people litter by sticking chewed gum on places or throw it on the floor, etc. Or something like that. I think that was the logic.
I hate finding gum on the underside of a desk. Especially if it's pretty sticky. It's super gross. And I always find it because I'm touching the bottom of the desk. And it's just... gross.
dog vomit - never stepped in it but have had to clean it up - yuck- and cat hair balls _!? What's up with those? They are worse then picking up an owl pellet (hair ball) by mistake and it breaking open. (now, if I had gloves on that might be scientifically interesting....).