Er, why do standing locks not work?

A lot of sporty types say standing locks are very low percentage techniques. I haven't fought in a sport yet, so I'm interested in why this should be...

I've used locks from aiki in all speeds and levels of contact sparring in karate and kungfu... successfully!!!

By successfully, I don't mean I've snapped anything off, just that it's destroyed someone's body structure enough to then stick some serious striking damage on them or to lead into a throw. Occasionally it's wound up dropping them like a sack of potatoes.

I also have partners in aiki who've used locks very effectively in a variety of street situations...

so...

why do standing locks not work?

Just asking...! Especially those with ring experience, or who practise chinna or locking arts...