People don't like to cook.
Or to put it another way, people don't like to cook all the time. Sure, it's great to put together a meal for a special occasion or, if you're like me, you're fussy about how and when you like your meals prepared, but there are a lot of times when cooking just isn't convenient. Like when you haven't bothered to do the dishes for a week. So, it's only natural that the idea of a machine that does the cooking for you is so amazingly attractive. Don't believe me? Ask your friends how many have a decent chef's knife and how many have a microwave and see which wins.
This idea is so attractive that it became something of a cliché. That's why it shows up on Star Trek ad nauseum (sounds like a good series title). The Jetsons would be lost without one, as would any self-
The only problem with the food machine is that when it reaches it's logical conclusion, you've got a vending machine.