> I'm not sure if this isn't as common as I think it is - but what's wrong with typing `ip` into a terminal

Well, for a start, `ip` isn't enough to give you anything. You'd need at least `ip a` or `ip r`, but then you'd have to already know that or go hunting in the manual (the `ip` help really is pretty bad). For something you might only need once a year (and will forget before you need it again!), having it in the GUI is very valuable.