You right.How do y'all know this? My understanding is the vast majority of LCD screens are a glass sandwich.
Capacitive are glass - for capacitive touchscreen to work, there is wires manufactured on the glass itself - this up to just recently was possible on glass only so this is why it is glass.
Also LCDs are from glass for the same reason, there are already plastic film LCDs but are pretty new (like flexible amoleds and flexible epaper)