Some people grew up eating that shit and it provides them with a sense of comfort and familiarity.

That’s exactly it. It’s confort food for a lot of Americans. I grew up in a different country, where home cooking was the norm and fast food was considered a huge waste of money. I of course tried it when I got my own money, but there was no reason for it to stick with me. So now fast food places don’t even register as an option for me if I ever find myself needing to eat from outside the house. But I’ve seen my friends in the US talk about fast food, their eyes gleaming talking about the Whatever Burger at Whatever Fast Food and the Whatever Taco at Another Fast Food and always get the Whatever Sauce at Yet Another Fast Food. The same way they talk about Twizzlers or Twinkies or other absolute junk that they would never touch if it didn’t bring them back to their childhood.