Exactly. I can't see a use for a "Find all Polls" function unless polls are a specific focus on the board in question. In that case, I think it'd be more effective to group them together in other ways.
IMO the idea is great, because in order for polls to show useful results, they need more than just a few votes. One solution is of course to have a separate subforum for polls, but "adding Is a poll" as a search condition would be better.
A separate poll subforum sometimes makes sense, but the best solution (in order to get enough votes) is sometimes to place a new poll in the subforum about the topic the poll is about, which is why I like the idea about adding 'poll' as a search criterion.