Most of these are pretty obvious, though I'd rather recommend avoiding slots unless they show specific RTP rates and are provably fair.
Slots are often one of the lowest RTP games at the casino, and there is absolutely no skill element to most of them, hence why they're not particular on my list of interests.
That being said, there are some with cool themes, but that quickly gets boring after a few runs.
But not everyone knows sports betting or poker or any other games that "require skill," as you said. This is why slots are found by some people a good game for betting. The simplicity of the gameplay makes gambling just a breeze. Yes, the RTP is low, but the thought of hitting a big win on a random spin is attractive enough to make you take a shot at the jackpot, esp. if the slot has a progressive prize pool.