So a lot of us have heard of this, but nobody thus far can show us where it says to take two pair with you to the DAME? My last medical, I didn't get told, I didn't take two, guess what happened? Nothing.
While I do carry a spare pair, and I suspect most pilots do likewise, I also use a flight helmet, and while I could remove my glasses if say a lens fell out, there is not one chance in hell of getting the spare pair of specs back on in flight. I've also not had a spectacle failure in over 50 years. i.e. never.
Nice research Clint.