Its a way to game SEO, by having links in other places it can make their homepage show up higher up a search result. There could be other reasons to as well, it can also be testing of capcha defeating software. Another thing to consider, these scams are intentionally set up to only catch the "dumb fish" as it were, they don't want to waste time with people who are likely to back out. But there are plenty of people who are not so smart that might be enticed.