It is both a good and bad thing that applications are skinnable or extensible. Being skinnable or extensible means that an application is well written enough that there’s a certain level of abstraction between the interface and the application itself. It also means that users can customize it to their preference, and implement their own features on top of what’s available.
At the same time, when the first thing most players do after installing World of Warcraft is to look for a custom interface at one of the humongous sites dedicated to providing them, and people constantly talk about a list of “must have” addons, it becomes obvious that the default UI is sorely missing much needed features that should have been available right out of the box.
This is not a problem unique to WoW, it applies to any application that presents themselves as being extensible. The same charge has been levied at Firefox again and again – why don’t the developers look at the top five extensions people are using and incorporate them directly into their product?
Well, some times, they do. Though not to the extent of the UI mods that are out there.
Blizzard, and SOE have both changed their UI’s over the years to incorporate things that people add to their mods.
It’s hard to please everyone, and lots of folks enjoy just using the base UI that doesn’t require a bunch of new fixes every time the game updates. It’s a lot of work.
Kudos for those out there who do dedicate their time to bringing wonderful mods to people to use.