There are a lot of incredibly valid reasons to refuse to date someone. A lot of them fall under the major red flags umbrella, you can tell they're not thoughtful in the ways you need, there's no connection or spark, you want different things from life, they exhibit disturbing behavior early on, and the list goes on.
Then, there's an entirely different tier of smaller, far pettier reasons people refuse to date someone. Some fall under the more shallow umbrella of looks-based reasons, but oftentimes these turn-offs are connected to very specific pet peeves or ticks that push buttons like no other.
If you've ever rejected someone for an admittedly petty reason and felt silly about it, or you've been on the other side of that rejection, then you may find catharsis in this popular Reddit thread full of petty reasons people stopped dating.