I wear contact lenses. If I could instead wear lenses that continuously monitored my glucose level and it didn't cost me anything extra, and they still gave me the visual acuity of my normal lenses, why wouldn't I use that? I already wear them every day so for me, it requires zero effort.

Having to get urine samples regularly, or worse, blood samples, is a LOT more work on my part (not to mention painful for the blood samples), so it's not something I'm as likely to want to bother with.