When I was growing up, it was very common that people didn’t eat in other people’s homes. I don’t know if it was an out-of-town thing or a generational thing, but I don’t notice that as much anymore. Personally, I have grown very lax (I’m not saying that is good; just stating a fact).
I remember one kid who wasn’t even allowed to drink a cup of water in anyone’s house. Her parents were concerned that if she drank a cup of water in someone reliable’s house, her younger siblings might follow her example and eat something problematic in someone’s house whose kashrus was questionable. Her father is actually a known Rosh Yeshiva, although I didn’t realize it at the time (and maybe he wasn’t yet).
If you don’t eat at anyone’s house, then you don’t have to worry about insulting anyone. But it takes a lot of discipline.