Its more about "convenience" and access--there are places like college dorms where you might not have a stove or oven. You either ate at the cafeteria or got take out/food that you can microwave. You used a hot plate, and could have an electric kettle, but that shit isnt really easy to make a full meal on. There was a community kitchen in the building where they also had a community tv, pool table, a lounge and the laundry machines and shit, but you dont always want to be cooking your own food out in the community kitchen and have other people around, or to be that one dude who smells the place up and it's kind of embarrassing.Is it really cheaper to buy packaged food in burgerland than making your own from base ingredients?
A lot of people move out of the dorms pretty quickly or just already have an apartment, place to rent or stay, roommates, whatever, but there are a lot of people who just live that life and dont think much of it.
Other than that, or just specific scenarios, or people just trying it out--it is about the same price, buying ingredients is cheaper and you get more, but I dont think the average supermarket consumer consideres it to be a big enough price difference per serving or whatever that it's too big of a deal, unless you really are crunched for money.