Is it already winter? I tend to wear flip-flops all year, except on the few days it drops below freezing (seriously, rain runs through flip-flops and I couldn't be happier). Honestly, I've been keeping my nails painted because a few paint jobs back, my nails got dyed pink by some purple polish. Also, two of my nails have been damaged in the past so they have cracks & crevices that I can't get the polish out of. Long story short, my toenails are always painted because they're very ugly without the polish.
Even if I wore shoes, I'd wear the nail polish. It's fun, it's for me.