I am sure many fighters pass up submission openings, but they are not doing it to please the rednecks in the crowd. For example, if you pull mount an armbar is often open. However, it is much lower risk to sit on the guy and punch him in the face. If you can finish your opponent from there, why go for the armbar? This is MMA not BJJ.
As for the whole fighter stand up thing. I think fights without stand ups for stalling and time limits are unbearable to watch. I would rather see some average striker GnP his opponent than watch one of the worlds best grapplers lay in guard for 45 minutes. If a fighter is active from the guard, he will not be stood up.