I started using them on Twitter back in the day to get a better idea of my audience. That changed when a friend of mine saw a poll of mine and said, I have to get back to my desk so I can vote in your poll.

There's something about polls that encourages engagement, and that's why I was lobbying for it a few years ago. Most of these sites have way more lurkers than posters/commenters, and polls are a good way to bridge that gap. For instance, most of my posts don't get more than 10 comments on average. A poll easily gets 30 votes at least.

Essentially, it's an easy way to get people to not just read, but participate.