After a dog goes to the bathroom, they can’t simply grab a roll of toilet paper and use it to wipe with like a human. Asking why do dogs lick their butt is almost as bad as asking why human’s use toilet paper to wipe. Just like us, dogs want to be clean. They don’t want to be walking around with poo stuck to their butt when they are around people. Some dogs are quick about this and others may take longer to get the job done. If you don’t want your dog coming in from its bathroom break smelling like a toilet, let it clean itself the only way it knows how.