“I believe certain families have always had this custom of not eating outside their own home, with limited exceptions of certain people they do trust.”
Im not sure what you mean by “Always” There is a halacha of eid echad neeman beyisurin there is no asterisk that not everybody has this minhag. BTW, Almost By definition all customs didint always exist but rather developed over time.
” This is not exactly a new phenomenon,”
Depending on how you define “new” Im fairly certain it is. I would absolutely love if you can provide reference to such a hanhaga more than a century or 2 ago.
See Syag’s accurate comment.
” and I don’t think there’s been a real increase in the numbers that follow this chumra.”
On this I know for certain you are mistaken as I know people who have adopted this “minhag”
LU
you correctly point out changes that led tio this shift. both of which I mentioend as well.
However this is the case for All of the shifts.
For example Zionism, I assume you view that as a change. however it can (and is) easily be argued that it is a change due to shifts in the world that allowed for it.
Or as you put it (And I whole heartedly agree)
So it’s not necessarily about the ideology being different but about the situation being different. The same ideology calls for different responses to different situations.
This is true for every change that takes place including mass kollel, maintaing a certain levush, Zionism etc
Which is why it is silly to say charedisim is the “default” and all other streams are changes.