Dave Manby wrote in
:

There is this strange one in France where the floatation of pfd you
don't have to wear (unless in a commercial situation) depends on what
craft you are in. Bigger floatation for rafters than for canoeists and
kayak paddlers. Why does it make a difference what craft you fell out
of!

Maybe it more to do with what craft you're more likely to fall out of.