I started road riding 3 years ago after 16 years of mountain biking. The only fall was due to not being clipped in. Unclipped for a stop and then didn't have to. Put pressure on the pedals and the foot slipped off. Luckily the fall was onto grass.

But give it 3 months with clipless and then ride a bike without them. The foot will slip all over the place- bump in the trail or road and the foot will bounce off the pedals and you will also find that the legs ache. I would almost say that riding platform pedals is dangerous. I would definitely say that when offroad. Tieing yourself into those pedals will give you more control. Slow technical bits and you want to move the bike around and you only have 2 contact points as you will be out of the saddle. Lose one of those and you soon find out how much control comes from a simple thing like your feet..