Never.
- As PPs have said, if you live a long way away from anywhere selling fast food, it's MUCH easier to do something quick at home.
And, as another PP said, the taste is so often very, very disappointing.
- I don't eat meat but my DH does. A nasty recovered industrial meat and starch burger ( we all know what Jamie Oliver called them) in a boring, flaccid white bun costs so much more (according to this site: www.fastfoodmenuprices.com/uk/mcdonalds-menu-prices-uk/ than a similar-sized portion of nice grass-fed steak. I can cook that for DH in 5 minutes - cut in strips and stir fried with onions, peppers or mushrooms, garlic etc , or flattened against a really really hot cast-iron pan. It's so much more healthier and - I'm prepared to bet - tastes an awful lot nicer.
At the same meal, I'd probably have an omelette. With cheese or mushrooms etc. Costs even less and takes about 2 minutes to cook.
I really, really don't want to sound smug, though I know many people will probably think that I am being so. FWIW, I but the meat in fairly large quantities, pack it in individual portions, freeze in and then take a pack out of the freezer before starting work in the morning. There are of course many other quick, tasty and healthy alternatives. I just think we've somehow all been brainwashed to think that nasty industrial food is somehow a treat.