[bri3d]

The tools do include that functionality, called Interface Builder or the Storyboard Designer.

The editor on its own is fairly nice to use these days, but it outputs obtuse XML and has a propensity to edit parts of the layout XML file that weren't actually modified. This makes source-control level collaboration and especially code review very difficult. To make things worse, for a long time the tooling encouraged putting almost all UI into one giant "Storyboard XML" file, guaranteeing confusion and conflicts.

The editor was also quite slow and crashy for years which drove the proliferation of these libraries and the "don't use the storyboard editor" meme accompanying them. It's gotten a lot better in the last ~2 years and I haven't had a crash in heavy day-to-day usage for quite some time.

If Apple could improve the XML output format to be easier to review, eliminate the serialization/deserialization weirdnesses, introduce a visual diff-and-merge tool, and improve the performance just a bit more, the Interface Builder would be excellent, but as is, I see why a lot of people don't like using it, especially on big projects with many collaborators.