Additionally, vendors just want to ship software. I guess that's their version of getting shit done. For better or worse, functionality sells most software. The stock UI is an afterthought, let alone possible customizations to it. Spending time on features that at best don't sell, and, at worst, can introduce bugs, is a non-starter for most shops.

Maybe Microsoft/Apple are big enough that they can (and should) handle it, but I wouldn't generally expect this type of gold plating.