IMHO, I think they're just another tool to have in your box of tricks. There are things that we have in our arts, that we'll probably never do, yet we still train them and teach them, as its very possible that someone else may find a use for them.
There are locks in the arts that I study. IMO, I think that its important, just like everything else, to train the locks, with a resisting partner. Obviously, with anything, safety needs to be exercised, but its something that I feel needs to be done.
There was a question in that other thread that came up, about what we do with the badguy, once we've controlled him. If we were to do a choke, obviously we put them to sleep.

With a lock, well, thats a good question. We run the risk of pissing them off if we let go, hoping that they leave us alone, so looks like we'll have to follow thru with a break.
As I've said in other threads, no matter what we do, theres a chance we may get into trouble, especially if we hang around, but I'll worry about that later. At the moment, my safety is #1.