Right, John, a lot of eyeglass shops sell only plastic, and don't have an optician trained to do glass properly, but your opthamologist will direct you. Most people don't need them. When I was working I was chained to a microscope and other instruments of torture, and I was rebuilding (or trying to) watches as a hobby, so stuck with glass. We had some polycarbonate glasses without correction we used when we went to the shops where there was a chance of flying fragments, etc.   

Don't sucker for the latest frame styles for plastic eyewear which can be very expensive and give the shop uberprofit on uberstyle. Übercool! This is perhaps the main reason the fitter doesn't like to talk glass. Be sure to specify impact-resistant polycarbonate; some of the other plastics now being used are even more scratch-prone.