It is a cost issue, but also a quality one.
I for one, could not eat at cheap low quality places like Ponderosa 3 meals a day, every day, for 2 weeks. I think I might suffer digestional meltdown and also start up a few major health problems.
Even if you just ate breafast in (ie fruit, cereal, toast etc) and then ate out mid day and brought home a takeaway from wherever you would normally eat you would save, as restaurants routinely charge less for take out even if they are a full service sit down place- not tom ention what you save on tips. And getting in some chinese or Pizza, with the huge portions I find that usually feeds us twice so you get 2 meals for the price of one.
And I find that shopping, cooking properly and eating in is cheaper and healthier unless you stick to places like Steak and Shake or the pretty poor buggets like Ponderosa. For a start on the health front eating in means you won't get fries with everything.
At it's most basic, s/c means you can wake up, have a cup of tea and a piece of toast while watching the sun rise w/o having to dress, go downstairs and pay high hotel prices for a cup of tea. And it means you can bring left overs or takeouts home from a restaurant and eat them next day, heated properly and with plates and cutlery.