I think it just might be because the seal around the glass would inevitably fail from constant thermal expansion during normal use, thus leaking all over the damn place.
‘Just hot air’ is a bit of an understatement. Mine goes to 500°C during a cleaning cycle. It physically locks the door so you can’t open it when it does this. My dishwasher I can open at any time.
Fun fact you can hack a self-cleaning oven to use the hellfire temperature of 500 ° F to make good ass thin crust pizza!
you have to figure out how to bypass the door lock, use a pizza stone, and put the pizza as high up in the oven as possible. but you can get a damn good thin crust pizza with enough creative engineering and some experimentation.
recommended to try this project in winter as it dumps loads of heat in the house lol