Or the grain feeder. Neither do most people. Any open object is meant to be climbed into. Never mind the size of the object in comparison to your size. Also never mind that the object may be harder to exit than it was to enter.
Trailers are more fun to get into than they are to get out of.
Horse hair bears a striking resemblence to grass. So does people hair. All objects have the potential to be edible. Much tast-testing and chewing is required to discover this potential. Other horses make interesting noises when you nip them.