Also, I assume the main reason most people (including myself) wear contact lenses is because of esthetics, right? Well, when you're in the field, you look bad and smell bad and are not very likely to run into a willing member of the opposite sex. At least not a human one. So, the main reason to wear contact lenses being gone, glasses are good.
Though, wearing glasses and having to do a gas drill is a bitch... Throw glasses away, perform "regular" mask procedure, try to find glasses without seeing them. Especially fun at 3am when your guard duty ended at 2, and you got artysim and grenades and all that fun stuff exploding around you...
Admittedly I've only been in the "field" once, IE Farnham, but it's already enough of a female dog there, I can't imagine in a real operation.