The best way to attract a player isn't by showing them someone playing well, it's by showing them someone playing very bad
Because these ads show demo play (usually of puzzles) where the player is making obviously bad decisions, and watching it is sort of like seeing a dozen objects in a row, but one of them is completely askew, and there's an urge to straighten in out a bit.
I only noticed this after seeing a bunch of ads recently for perhaps a dozen different games, and realized that I felt somewhat uneasy when they came on instead of simply impatient, and eventually. I tracked this feeling down to the crappy gameplay phenomenon. And once I realized that was the issue, the unease went away.
Further reflection made me realize I'd been much more tempted to download those games to "do it right" than other random games that didn't seem to use this tactic. It was actually when I broke and was about to download one that I had the realization, basically "this game looks awful and tedious, why am I about to download it?"