Trade dress is about what the average consumer sees and perceives? First to market matters here because even with a lot of patents covering the outside of the product there's so much more involved in trade dress. Therefore it doesn't matter that Apple copies, they were first to market and were copied in the market in a way that would be considered similar by laymen. Lawyers would have a much higher/harder standard of similar.
Trade dress infringement also doesn't apply if there is only one way or a "best way" of doing something. The law provides exemptions, so that one company doesn't have to make an inferior product just to avoid trade dress infringement.
A lot of what apple was calling "trade dress" was arguably just the best most obvious, or cheapest way of doing something--bezel etc...
