Earlier quoted context omitted.
Glass lenses are only good for spherical prescriptions. If you have astigmatism, you need an aspherical lens, which cannot be shaped in glass.
I've owned several pairs of aspherical lenses made of glass, ground by competent yet hardly exceptional shops. Only in the U.S. I found people uninterested in selling me glass lenses--exaggerated mimicry, "but they'll be so heavy!", etc.
Yeah, they are. If you only have say -2 its no big deal. I have -4 and with heavy glasses (I used to wear such) I get pain in top of my nose rather quickly.