On the flip side why would a non-developer bother to install Xcode and learn IB when they can export their ideas directly from Sketch/Photoshop into clickable "prototypes"?
For large changes, it can be unmanageable. But large changes are hard to code review anyway, so we try to avoid those.
At work we had two teams who had very different opinions of IB's usefulness. In our case, it was based on the nature of each application. IB does not provide much value when the majority of the screen is dynamically determined: different elements based on user preferences, locale, document contents, etc. The team that disliked IB, their app was almost all dynamic (and lists/tables, whose cells were also fairly dynamic).
Our team, on the other hand, had a very static UI. It had very little runtime customization (other than the contents of labels, images, etc). We loved IB.
And then child ViewControllers came along, and made it easier to mix static/dynamic content on the same screen.
I haven't used UIStackView yet, but I suspect it also will help with screens that contain dynamic content.
While I absolutely hated AL at first (and the IB just plain sucks) I do find it very time-saving once it clicked.
Whether it was written down or not, it seems like a good idea in theory. The old, stand-alone IB wasn't all that hard to figure out (though struts and springs might bring the death of your sanity). Get the UI all prettied up, and hook up an implementation behind it. Not that I've ever seen that in practice, however.