This is one stereotype about gamers & tabletop/card gamers especially that is just so thoroughly true and highly cross-cultural. Any in-person events within the "nerd culture" halo exhibit this phenomenon as well. You'd think "oh just do a smell test on people entering the venue and bar smelly people from entering" but it doesn't work like that. Their smell develops over time as they sweat and the bacterial colonies on their bodies & clothing activate. Hygiene can't be a one-day thing, you have to keep those clothes from getting smelly for as long as you own them. Barring actually forcing people to take a supervised shower to ensure they soap their ass, put on deodorant & issuing them a clean set of clothing on entry this will always be a problem.