I bought a Leatt when they first came out, wore it a number of times, but then i thought about it, so i don't wear it anymore. WHY?
Because they actually ( in the real world) cause more damage than they prevent. Someone crashes, breaks a collarbone and shoulder, and the ambo says lucky you were wearing a brace. Everyone talks about Baily and Chandler, ok, how man trillions of laps have been raced over the last few decades.
That's why i don't wear it anymore, haven't needed it the last 35 years. I know guys who take over half an hour to get changed into their riding gear.
There are no proven cases. When the day comes when i know what type of accident i will be having that day, i will dress accordingly.