Video about self defense applications for Leg locks;
Not the best sound quality, and I thought the first demonstration using the back mount wasn't very applicable for self defense. However, the open guard application was pretty solid.
So given they're strong self defense applications, why aren't leg locks more widely trained (even in grappling arts)? They're efficient, dangerous, and can be applied from a variety of positions.
I think it is two fold. The first is noted in your own premise they are more dangerous than other maneuvers, both for the person attempting to apply it and the one on the receiving end. Second, while I haven't studied a grappling focused art in years, those that I did study, at least in the way they were taught to me, also had in mind the ability to disengage rapidly if necessary and the maneuver makes rapid disengagement, not impossible, but more problematic.
Finally I believe that it could be, in terms of actual self defense application it is of limited value, from a legal and practical standpoint. In terms of legal...
In a real self defense situation you are not going for a submission, you are looking to end a threat. You can end the threat via that maneuver depending on what other techniques you apply along side it/how far you go, but intention choking out another person could easily be seen as disproportionate use of force if you were only addressing a misdemeanor assault as it has the risk of of death or permanent disablement. If you applied other locks and a joint was broken the same concept could apply.
In terms of practicality...
1. In say a bar fight type scenario your opponent's friends, if they have them, are coming to his aid and you are now rather vulnerable to them, and if you go to disengage you have the issue I note above.
2. Unless you are VERY skilled at it applying it in the chaos of a real fight in and of itself is problematic.
That all said I do actually see the benefit of training in it, even if only to understand the mechanics of it so you can avoid/escape it as the still growing popularity of MMA means it could be used against you. That said not that many instructors teach things with that perspective in mind and if they aren't training it with the specific intent of use, sometimes they don't train it. /Shrug.