Is it possible that he is no longer steady and/or coordinated enough to keep his feet on the pedals of a regular bicycle?
You are right about the toe clips. Is that what they use in the Tour de France?
If you can’t keep your feet on the pedals without clips, you are not in shape to ride a 2-wheel bike, period.
The clips that Biden used are where you slide your toes into sort of a little basket. You remove them by sliding your foot back out.
In the Tour de France, they wear special shoes that snap right onto a special pedal.