Question on making homemade bread?

I'm just curious. I have a recipe for white bread from a Betty Crocker cookbook that I have used since I was a teenager (I'm 54 now). The bread turns out great; no problems there. My question is about one of the ingredients. It says you can use 1 3/4 cup of water, potato water, or milk which has been scalded and then cooled. Why does the milk have to be scalded? I've always done it and just now wondered (shows you how quick on the uptake I am!!). The milk is NOT being used to dissolve the yeast, that is done in warm water before the milk is added. Plus, if you choose to use the 1 3/4 cup of water or potato water it is not required to be heated in any way. Just curious after all these years....thanks.