I suppose you medical guys don't approve of wearing thongs (flip-flops) on a bike either, even if they're double-pluggers.
When I was young and stupid (now I'm old and stupid) I wore thongs while riding on a very hot day. I was also wearing shorts and a T-shirt, but let's not go into that. I only ever wore thongs that one time because I had two footwear related mishaps on that ride.
The first mishap was when I stopped at the lights in the city and put both feet down on the road while waiting for the green light. It was such a stinking hot and sunny day that the bitumen on the road surface had partially melted and was sticky. When I took off, my thongs stayed stuck to the road as my feet were yanked out of them. I pulled over on the other side of the intersection and tiptoed back in bare feet on the hot tarmac to peel my thongs off the road. I put them back on my feet and continued on my way.
A little while later I ended up giving my toenails an unexpected trim while cornering. The toe of my right thong touched the road and got folded under the footrest, pulling my toes down onto the road. Luckily no permanent damage was done. Just slightly ragged looking toenails, some gravel rash and a bit of blood. It all healed OK.