Seriously, that's the question.
I prefer to wear glasses on days when I'm not interested in wearing my contact lenses - either I wore them too long the day prior or I'd rather not be bothered. My optometrist said that my eyes are really dry and I need to invest in some re-wetting drops; until I remember the next time I'm at Target I've been making good use of my glasses. I love them so and would wear them everywhere if I could - but at the monetary rate they went for I am simply too afraid to think about riding my bicycle while wearing them. What if they fell off? What if my vision was so sharp that I got a headache? (It's happened before.) I can barely see without the aid of something, so to not wear them is not an option.
I happened upon an amusing interview from ESPN, talking with bespectacled BMX-ers about their experiences and perhaps considering alternative options. Naturally, some ride with; some ride without. Some say that as long as you're wearing a helmet they should stay on - something I never thought about, but it completely makes sense. Sadly, I can't find the continuing article that details experience of "some of the guys that used to rock glasses [who] have since moved on to other options", but in the meantime I guess I'll just accept that if they can wear their glasses while doing tricks, then I can wear mine while riding uphill both ways.
Now that I think about it, I could always invest in a glasses strap, perhaps one in a deep violet hue. Oh yeah, I'm totally feeling it now, especially since (per one of the guys) "when you're riding, [glasses block] out dust and debris from your eyes and you look sexy". Something tells me that I can function comfortably within that advantage.