We don't let blatantly false ads run on TV. Why is it so hard for Facebook or Twitter to do the same thing?
A tv channel has like 6 to 9 slots per 30 minutes of content and most of those slots have the same ads playing multiple times in a day. I would guess that there’s at most 1-2 hours of unique ad content for one channel per week to review.
With user generated content and thousands of unique ad slots, using humans to verify is prohibitive.