The key is they have an absolute ton of employees in the restaurant (a busy McDonald’s might have four or five, In-n-out can have double or triple that. I’ve seen other fast food with two employees, never an In-n-Out) and they work exceptionally hard on specific tasks.
They also only deploy in areas where they’ve determined they’ll be able to keep the store busy enough.
What they don’t understand (until explained) is that what we get in a European countries are just a small selection of big franchises (McDonald’s, Burger King, Starbucks etc) and maybe a handful of other ones. In America there are dozens and dozens of restaurant franchises where you can eat for weeks each time in a different fast food restaurant in the same city without going to the same place twice. This is what always amazes me as a European, that huge amount of choice of everything you can have there.
These people acting like "everone knows it" essentially have the same world view that the entire world that matters is Southern California.