on SUPs your feet stay at the same place for hours, melting the wax and brusing your feet if on a hard surface.
I used (thin) pads on my prone surfboards, no wax, because I was often surfing rivermouths and wax got clogged with mud too fast. It is so great to have perfect traction and no wax messing everywhere, and jump in the water directly out of the car, but:
- forget surfing topless. You would get insane rashes fast.
- wetsuits worns out faster as we lay prone on the pads (not an issue with SUPs)
- it got out of fashion after the nineties
- I actually missed the smell of wax in the morning
- some pads (open celled ones) get soaked with water and are heavy when wet. not noticeable on SUPs, except the very light ones
- most prone surfboards are not durable, people change them often and the price of pads become an issue. Again, SUPs are more durable. (My surfboards were Epoxy pioneer Gerard Dabbadie - Superfrogs -, not a compression dent after 20 years of use)
The last 2 reasons also apply to the featherlight contest SUPs, this is why most of these boards do not have pads. A good compromise is small pads whete you stand and on the tail, wax elsewhere.

Note that I now use wax on my surfboard, since modern waxes do not melt anymore in the van.