What else am I missing here?
The problem with SMS verification is that sometimes you don't have your phone with you. Unlike a 2FA google authenticator where you can install it on your PC, tablet, phone or whatever device that supports it. Though, I would say it is a layer of security that would not really be hard to crack like you said. An SMS verification is much more secure but give a lot of hassle in my opinion.
I'm not sure if I'm quite correct on this (I just vaguely remember something like that) but mobile operators (at least some of them) may allow you to access copies of sms sent to your phone through their online services. Thus if you have this option enabled, you can see the confirmation SMS codes even without your phone nearby. Regarding GAuth, its use might be really counterproductive if Google left some hole in it, either intentionally or inadvertently...
So if someone finds it, the app itself could potentially lead to money loss