why dont people ever use the pin the biceps, knee thru the butt guard break in mma?

[DMcKayBJJ]

I think it is because if an MMA fighter has managed to stand up in the guard with his opponent's biceps pinned he usually starts punching, and then the punches open the guard quite by themselves. Keeping your guard closed in MMA vs a standing opponent is generally a bad idea, and if he's pinning your biceps at the same time then you're REALLY in trouble unless you switch to an open guard right away

Stephan Kesting
www.grapplearts.com

Yes.
Some would argue that keeping your guard closed in straight GRAPPLING vs. a standing opponent is also generally a bad idea, vs. opening the guard and defending/attacking that way.

 

[Enron Exec.]

cant do it when your gettin punched. you will have to let go of there arms when you break