dressing up pets for halloween

Do I have to wear this?
Do I have to wear this?
Do I have to wear this?
Why do people dress their pets in costumes for Halloween? The poor animals always look downright miserable, and yes, while they look cute and funny to us humans, I imagine that the other animals in the neighborhood snicker and make fun of them when they see them coming down the block -- dressed as, say, a SPIDER...