I am a very good baker. But when I need to make 200 brownies for some bake sale type thing i am not going to spend the ££ I would normally spend to make them. I wil buy box mixes because they are cheaper than the ingredients I would usually use, especially with my discount, and they are a hell of a lot easier to make in bulk. I am not buying real butter etc when the brownies are sold for less than it cost me to make them!
In my family we have several disabilities that you wouldnt even guess at if you met the people concerned and they use preprepped veg, box mixes etc because frankly a nice dinner is not something that needs to be "earned" by standing in the kitchen for hours.