For one thing, we have three couples on the show, and while there’s no rule saying that one or more of these couples can’t break up, it would seem odd to suddenly have Penny, Leonard, Howard, Bernadette, Sheldon or Amy around without their significant other of several seasons.
I think we can all agree that Steve Molaro is absolutely right when he says that, should one of the seven stars decide to leave, things would be super “different and weird” on The Big Bang Theory.
It’s true that all of the guys were around before their female counterparts were introduced as romantic elements, but those three couples are too much of a unit now for a breakup to be a realistic, or welcome, change.