I don't know a single person who has ever found a scholarship on those sites that they couldn't have found otherwise (like the big scholarships like Coca-Cola) so what's the point? You're just going to get spam.

Yes, they do. I wrote an answer earlier explaining why it makes more sense to apply for local scholarships than for big national ones. You have a better shot at winning a local scholarship and sometimes, you can only find them through your guidance counselor or through these sites. Go read my answer at:

http://www.prepme.com/answers/question/what-are-the-easiest-scholarships-to-win