My dd and I just came back from a prominent D1 softball team and their camp, and this very question was asked. The coach's response-the NCAA should make the pitchers wear them as a mandatory device. They are the only player who should be out of defensive position at the crack of a bat. THe person who asked then asked, what about the corners. His response was mostly noted on this thread except for one....he also stated not only the bat manufacturers but tournament directors. The reason tournament directors and probably one of the biggest complaints of a tournament----field maintenance. He said a properly drug field after every game prevents the bad hops that allot of players take. But because tournament directors don;t want to pay for the additional staff to drag fields, they're taking chances on a young girls face getting tore up. He also said then if insurance companies go after the tournament directors, maybe then things will change.
Well, that parent (apparently big on face masks) asked, what about the corners. He said they shouldn't need them either because you wouldn't put your 3rd basemen up 1/3 of the way up the line for the 3-6 hitters (something along that part of the line-up). He said if the #4 comes up to bunt, let her have it. Most likely, she's too slow to make it to first with the 3rd basemen charging and firing a quick strike. The coach did counter to the parent, how many times will you see the #4 batter bunting? The percentages say not a lot.
He did stress the younger ages should wear them until they learn their smaller motor skills.