Memes

So, a few use cases, but it tends to boil down to convenience.

Some people work from home, and don't have time to go get food, nor cook anything significant between meetings, and they're just tired of cold sandwiches and microwave soup.

Spending however long traveling to and from the restaurant isn't always a valuable use of time compared to whatever else you were doing.
If I'm playing games alone or with friends, I'd rather do that than drive around for half an hour.

If you've got kids, loading and unloading them into the car can be a chore.

Or just plain "comfy, don't wanna leave".

Delivery is a convenience that people like. Companies switching to a service with more fees that drive the cost up so high is annoying.