because of the texture of the WW flour. For most things, if you use all WW, they just don't turn out very well. There are some recipes that use all WW flour, but if it's a recipe that calls for AP, I do half of each. I think that's what the WW flour bag even says...of course, others might do all WW...not sure. I bet someone else will come along and post who has more experience than I do!