I have the platform pedals on my (antique) MTB which I rode/ride mostly on the road. Back when I was riding the bike a lot, I also had a kid in a seat on the back so clipless freaked me out. I never had a problem with slipping off the pedal though. I did focus on good pedaling form which I would suspect has a lot more influence than being clipped in.
I did have some great (clipable) mtb shoes from Performance way back. They were a lot more helpful than regular tennis shoes, lot less general foot fatigue. My dog chewed them up tho when she was a pup(boo!) and I'm hoping to pick up some new shoes soon. I have some trail running shoes that I use now(saucony) that seem to mesh well with the pedals. I do like a stiffer sole. The Performance mtb shoes had nice deep hard rubber cleats that made grip easy.
But yeah, have always liked having options to positioning feet on pedals(or pegs on the dirt bike, feet move around a lot on those too depending on how much flexion you want for body suspension--more towards toes for more flexibility, back towards arch for stiffer). Helps with fatigue on long rides, and the repetitive movement injury thing.

