On Dartmoor in particular, the ground is very boggy & there are hundreds of streams to keep crossing. It's much easier to just walk through the streams than worry about rock-hopping your way across - one slip & Smack! Splash! Ouch! My camera! Waterproof boots tend not to stay waterproof when the water gets up to mid-calf & beyond :-)
I also have long waterproof socks.
I believe a decent set of gaiters will also keep water from getting in via top of boot.
I don't have an issue with hot sweaty feet, so getting them wet will simply mean very cold feet. So no chance of shoes drying out, particularly when temp drops. I ended up going through a bog today whilst out on bike. Waterproof socks kept feet lovely and dry/warm when my summer cycling shoes shoes got sodden.