Joint locks, like OC spray, work really well on LE students who have an incentive to comply to pass the training module.
They don't work so well on people who are assaultive, drunk, high, adrenalized, mentally ill, or a combination thereof, and who will feel no pain and will not just stand there and let you put it on them.
Real people wriggle, wiggle, pull away, spin, flail, flex in unanticipated ways, are sweaty, wet, bloody, head butt, kick, spit, bite, pull out weapons, and do many other things that make joint locks less than effective on the street.
Sometimes they can work enough to get the job done, though.
Those are my observations based on a combined 24 yrs in LE . . . YMMV