All true; but if one expects things like glass windows, spectacles/monocles, glass-based mirrors, magnifying glasses, and other such refinements to be a part of one's setting then it naturally follows that quality glass-crafting at least for small-scale items would be (relatively!) common in that setting. Astronomers' telescopes and the like are a different question, but I don't mind these either as a rare and exotic element in the setting.
I also want spyglasses to be somewhat easily available for their main users: mariners and sailors.
Note that for lenses I'm not talking stupendous quality here: a 2x or 3x spyglass would be fairly common (and, depending on quality, might not even be all that well-focused), a 4x is getting up there, and by 5x you'd be talking a) bloody hard to find and b) that 1000+ g.p. price 3e has for them.