the explanation, I think, is that, like their horrible chocolate, a lot of American butter is substandard, because of looser regulations; European butter has to have a higher butterfat percentage than American butter and those extra percentages add a lot of flavour. American butter is usually designed for cooking and, unless you go out of your way to look for the good stuff, it doesn’t add much to a sandwich.
This doesn't make sense - I know their butter is inferior their YouTube chefs often talk about using french butter which upon looking into is just butter here.
The issue I have is I was brought up on margarine of various types* *being in sandwiches only as an adult able to have actual butter have I realised how much better butter is. Kids and DH still prefer margarine in sandwiches and refer to it as butter even knowing it's not.
Nutella, jam and bacon sandwiches are only one I can think of that don't need butter or a butter substitute like margarine. I don't like salad cream or mayo.
This could explain why they don't "get" chip buttes or crisp sandwiches.