how many gliders went down due to medical
issues

Still better would be how many on the ground (3rd party) have ever been
killed by no-medical glider pilots. (Ha!)

I read in an interesting WWII history book "Blood, Sweat, and Folly"
(about that name but since given away & can't remember the author) that
describes many of the subtle screwups etc of pre-WWII -

"The reason so many regulations for private pilots were generated in
the '20s after WWI was the paranoia that most governments had to aerial
surveilance"