Why do mma fighters training bjj in their gi???

There a bunch of threads on this topic on the old forum. Here are a few articles about it.

http://www.no-gi-grappling.com/no-gi.html

http://www.no-gi-grappling.com/no-gi-vs-gi.html

http://www.no-gi-grappling.com/no-gi-vs-gi-2.html

you can do everything no-gi with a gi on. The Gi just adds to it, but if you say you're going to do no-gi techniques you can avoid doing collar chokes and grabbing the lapels and such. Even though I try to focus premierly on no-gi, I'll wear a gi every once in a while. I'm like 100x better with gi on so, I try to stay no-gi so I can improve.

I enjoy rolling in both and personally I feel that no gi is a far more technical game with regards to retaining control. People say that it's not technical because you can power spaz out of a move like a greased pig but for that same reason it is an insanely technical game for the person trying to choke out that greased pig.

My margin for error in no gi is very narrow. If I blow a control position they explode out I have to start all over. Additionally, all of the lessons you learn in no gi carry over to gi. If I learn to have a sick wizzer in no gi, then it becomes a sick wizzer with a lapel grip for no gi.

So far I've liked Dave Camarillo's explanation for training with the gi. As other's have stated he he argues that it develops a strong grip which can be used in no gi grappling. Many of his no gi judo variations utilize a tricep over grip with an underhook; a setup that is tough to work without a gnarly grip.

I train both, and only for grappling. Personally, I found that using the gi improved my technique as a beginner. Because I started nogi I feel like I still don't utilize the gi as much as i could be grips wise, but its just another tool that adds to your game. Also don't forget that any street clothes can be treated like a gi. May not be for everyone though. It took at least a couple months before I wasn't feeling claustrophobic in it!