In my experience it is a horseshoe, people that eat out for every meal tend to be either on the high end of the income spectrum and thin or the very low end and obese.

These are broad strokes, but my experience in rural America and in SF bears this out, rich people eat out very often and tend to be fit and the very poor also eat out more than average but tend to be obese. Everyone else is in the middle.

Also depends on the cuisine. Quite a few cuisines take extraordinarily long to cook, and at that point, you're better off just eating out to save time (if you have the money) than deal with those meal-kits that are either not sustainable, or healthy, or often-times, both.

In The Netherlands, the cuisine tends to be really simple, and salad-kits and meal-kits are extremely popular. The fanciest food that people 'cook' is often a soup or pasta, and I'd say it's extremely rare for anyone to make pasta or sauces from scratch.