I was a little surprised when I encountered this question a few times recently.
So, why should you wear a rashguard when you're doing jiu jitsu or grappling?
Well, because being sweated on by someone is pretty gross. We all know BJJ is a pretty physical sport as is. I can say I've been personally victimised by a beard or two in my mouth over the years.
It's important to remember that a lot of people who train may not be comfortable being sweated on, and it can be pretty intimidating if you're new or self conscious.
A lot of women and teens also train, and they might get a bit freaked out by a sweaty man trying to strangle them.
Maybe you don't care about wearing a rashie, but someone else you roll with probably does.
One of the joys of Brazilian Jiu jitsu is that we welcome everyone. So let's keep it that way.