Cages for double straps, do they exist?

i was going to post that keirin racers probably used clipless pedals, but then thought i'd check out some photos. weirdly, they don't! anyone know why?

single straps only though. why do you need njs cages?

i have some chrome doublestrap cages that i bought from 14. they look pretty much identical to the mks ones, except for the additional strap holder.

Teddy, I think they use clipless pedals, with a strap on top, for double security