People that are interested in cooking are going to have that stuff around, aren't going to be put off by 60 seconds of measuring things out, and like the ability to tweek the composition -- plus making things from basic ingredients increases the understanding of how ingredients work.
Also, for those of us without ginormous kitchens (mine is huge by urban European standards, tiny by suburban American), there's just a limit on how much stuff you can store that you can reliably recreate in under a minute.