I guess the real question is if you support universal healthcare backed by citizen's taxpayers or some fund controlled by the government, should this be part of the package or not? I don't think the question is if you want to make glasses free in a sense labor shouldn't be compensated. Nothing is free after all.
I think the lenses, basic frame, and the exam to get the prescription aren't different from any other medical treatment and should be treated as such. It's not much different to asking if dental care or mental health should be covered as well.
People who don't use glasses think it is an one shot thing, but depending on the problem you have, it's recommended to update the prescription at least every two years. which probably will necessitate lens change. If it has coating, this may need changing as well even if you can keep the old setup. Because of the costs, lot of glasses users may be forced to use the same glasses for way longer than recommended, having to endure eye strain and other health problems.
Lenses can cost a lot. Mine for instance, with no special features go for 200 bucks.