I don't know of a reason, it seems like it is slow cooking which is a traditional method. What is the inside of your crockpot made from? I would think ceramic/enamel would be best, I would avoid plastics, teflon coatings and metal. I don't know what they are made out of. I have been thinking of buying one, myself! Maybe when the weather starts to cool off again.

Slow cookers are mentioned once I think around the stew recipes. They're fine to use when you don't want to heat up the whole kitchen to braise something on the stove or in the oven. Just don't use those plastic bags inside.