I remember doing it for a few things. One problem I had was memes being troll-down voted. Users with multiple profiles would targetba few of my memes and downvote them back into submission. I think they took care of that after a long time, because I made five alt profiles once and tested it out. I tried upvoting my memes and the upvotes didn't register after upvoting it with the second profile. Same with the downvoting. And yes, I leave my email address each time.
But this site used to have an upvote/downvote bar that showed all the upvotes and downvotes. They obviously did away with it a while ago.