I get the impression that Reddit's ad network is just immature. We're finding that Reddit ads perform well and are cheap, suggesting that there isn't much competition for clicks. More mature ad networks such as Google's and Facebook's are better at reducing spam clicks. Google bought a company focused on this about 10 years ago, I'm sure Facebook put similar effort in. I'm sure this is something they'll work to impro…
Edit: Fun fact, one often undiscussed use for click-fraud was money laundering schemes, where people would own shitty landing pages with ads, and pay bot-net operators to click ads on their pages to legitimize money as "ad revenue"