This, they will then make a meme out of.
With no permanent record, that 0.5 sec would be totally unremarkable, not noticed, or long forgotten. With a potential continuous recording (even if only 10 secs at a time), they can review later, and extract those 2 frames where you look absolutely ridiculous.
These glasses just move the recording from a camera that someone will notice, to sunglasses that will go unseen.
Enjoy your meme fame.