it's not a family
you could trust your family
but here it's a bunch of strangers
anyone could be in your guild
you don't know whether it's a scammer or not
at least when you add friends via /f a
you actually like them and maybe know a bit about them
guilds are big communities
you can't know everyone
and most of the time
they don't even care about anyone
That's why there's a handy feature included in guild maintenance where you can kick the idiots out.