Because 99% of the time someone randomly initiates a vote it's for their own selfish reasons to exit without penalty. Whenever I've been in a group that genuinely wanted to quit an instance it was discussed before the vote was initiated. You'd think twice about trying to force 23 other people to quit the instance so you don't have to wait to re-enter if there was a penalty for it. Again - my solution would not harm anyone using the vote in the way it was intended. The vote button wasn't added so people can spam it when they want to leave - that's the leave button.