personally dont ever use them, but similar to the op, ive kicked around the idea. ive never seen any objective science backing a big benefit for healthy individuals (doesnt mean there isnt any, would love to see it though).
all in all, aside from food allergies/food choices/dietary related things... finding ingredients that enhances nutrient absorption/utilization likely has more merit then using enzymes that replicate what our body already is designed to do (which i realize is a very fine line of a difference, so hopefully that made sense).