Nice idea when dry, but not so good when you have mud and water knocking about.
I’ve got some pedals with rubber panels for grip on top. They are great when it is dry, but like riding on an ice rink when it is wet. When it gets cold, and the water that sits on the rubber panels freezes, you literally can’t keep your feet on the pedals at all.
Some BMX people use Odyssey Twisted PC, which are plastic flat pedals with pins. The pins wear out, especially if you bash them on things, although assuming you don’t do pedal grinds with them I understand they will last for some time. I don’t think they’re as good as a metal flat pedal, but way better than my rubber coated ones.
I guess shoes with big spikes would increase injuries on crashing, whereas surely the whole point of having flat shoes is that they’re easy to crash in.