You just said it all for me
When playing around and doing leves, having to wait for "not so fast responding" members of the group (to put it politely) to put up a BR and having everyone else stuck standing doing nothing is pretty dumb in my opinion. If the mob starts heading for the mages (usually me <.<) or someone is getting beat on too much then the BR is usually closed early out of frustration.
Yes, you could argue that the slower members should be excluded from doing the BR if they aren't capable because it is easy, but they are members of the LS and how can you learn unless you practice and try?

I can't bring myself to be cruel enough to shun players that may not be up to speed or as quick to pick things up in game.
Also, kind of off topic a little bit, but a lot of people I know use controller and the command /br off is broken at the moment

Yes you can close with the mouse or hitting "G" I think (?) on the keyboard, but it would be nice if they fixed this ^^