To wonder why people always assume a person

[User566112]

With a double barrelled surname have both their parents surname. I have a double barrelled surname both are my fathers surname.

Did you mean to put this in AIBU?

I can honestly say I have never given double barrelled surnames any kind of thought.

Do they? My children do (I don’t) but it’s my husband’s surname. I chose to only use one of the names when we married.

That assumes everyone does OP. I can't say i've ever though that or given it any thought either way around. People's surnames could be anything, including something they chose themselves and made up entirely.

I've never met anyone with a double barrelled surname so can't say I've thought about it.

All the people I have ever met with double barrelled surnames are both parents' names, but I wouldn't assume that were always the case.

The same way people assume my two surnames are middle name + surname.

No, it’s not my middle name, it’s my first surname and the one I actually go by. No, they’re not double barrelled. They’re two independent surnames.

People assume all sorts of things. I think they default to what is more common to them.