[La Forge goes back to work; Scotty follows slowly]

Scotty: Do you mind a little advice? Starfleet captains are like children. They want everything right now and they want it their way. But the secret is to give them only what they need, not what they want.

Lt. Commander Geordi La Forge: Yeah, well, I told the Captain I'd have this analysis done in an hour.

Scotty: How long will it really take?

Lt. Commander Geordi La Forge: An hour!

Scotty: Oh, you didn't tell him how long it would really take, did ya?

Lt. Commander Geordi La Forge: Well, of course I did.

Scotty: Oh, laddie. You've got a lot to learn if you want people to think of you as a miracle worker.

I'm an iPhone UI designer/developer and you can make a really nice looking app without doing any custom design work just by using the widgets that Apple provides. A good example of an app that was nearly all stock is Tweetie 1 for iPhone and it won an Apple Design Award. Apple has put an incredible amount of polish (single-pixel highlights and shadows, consistent sheen/gloss across elements, built-in animations for common interactions) into the widgets as part of UIKit, and then the apps that are included on the iPhone are also incredibly polished. This sets the bar very high and also gives a quality of UI design that developers can look up to and try to emulate.

The apps that Google built for Android (Maps in particular) are very clean and elegant but I would hesitate to call them beautiful or extremely polished. Google's design aesthetic typically eschews gradients, sheen, highlights and shadows in favor of a flatter, cleaner look and feel. Although Google's Android apps are well-designed, they don't look like a team of visual designers hand-crafted each and every corner like Apple's apps and UIKit widgets seem to be. Because of this cleaner, simpler aesthetic, the bar for "good-looking" on Android is a lot lower than for iPhone and it seems companies will cut corners on Android app UI design & visual polish because of it.

Another theory is that companies might feel that Android phone owners are more technical, more geeky, and thus "don't need" a really polished interface so they spend fewer resources on it. Once a few big companies release Android apps with a sub-par design, other companies see this and follow suit, continuing the trend forwards. Obviously this is a difficult stigma to get out of, but some companies are putting out great Android apps -- Gowalla comes to mind -- so there is hope.