Assuming you're interested in custom UI elements, visual styling in native iOS code is significantly more time-consuming than something like CSS (assuming an equal level of familiarity with both). A lot of apps just end up using static image assets for everything because it's that much easier and quicker. If the performance is decent and the pricing fair, this could be a big time-saver.

Of course it can be achieved using traditional methods. But this could be a much faster and more maintainable method of styling. Compare straightforward CSS files to XIB files, storyboards, and a bunch of images.

You can use a native iOS implementation. I wrote a demo app over Christmas break using Pixate and it was so easy to style. The only problem was that including Pixate caused a crash when I tried to removed the camera view controller so I had to redo the whole thing native.

That's when I realized the power of Pixate. My code got a bit more complex having to implement the gradient layers, borders and background images in Objective-C. I ended up migrating it, but Pixtae was definitely a lot simpler.

Nobody is saying it can't be. The draw is making it easier for people who are more comfortable with CSS, which is a lot of people.

It can and it is preffered. Especially if you dont care about iOS < 5.