Why do people click on those ads?
Now we need to dig deep and research the human motivation and psychology. However, the most speculative, but legitimate reasons are:
1) They can’t tell the difference between an ad and an organic result.
2) The ad seems like the most relevant result for their search query, as it is placed right on the top of the search results page.
3) The ad is so good it instantly catches their attention indirectly.