So, in my experience, it's less unhygienic, and more a problem with not covering up their natural smells. Sounds similar, different things. I'll explain me experience with TTRPGers.
All the ones I know who fall into the funk trap are autistic folk, and the issue isn't that they don't bathe, it's that they can't stand those strong chemical smells they associate with body washes and deodorant*. So they bathe, but they use mild soaps, soaps designed for children, or unscented soaps, and they don't wear deodorant.
Which creates a situation where the hygiene is okay, but the funk is still there, once they're all in a group together. One on one, you really don't notice, but get 10 folks in a room for game night, or a couple thousand together for an event or convention, and the funk becomes overpowering.
That said, I do know two that have just a general aversion to bathing, and consistently reek
*Edit to add
Also an issue with texture on the skin. One of my best friends is autistic, and he cannot handle the feeling of deodorant on his armpits. It tacks the hair down, it's apparently sticky feeling, and he just goes into total meltdown until he can get it off. He can't focus on anything else.