that is a good question. I'm sure a lot of them are defensive patents, but then you have the whole "App Store" name debacle between Amazon and Apple, and then I start to wonder...
Unlike with patents if you don't defend a trademark you will lose it. Trademarks and patents are different and I'm curious as to why you're relating them here.
but yes, a trademark is representative of a brand, and it's important for companies to control their brand image, especially companies who are constantly under surveillance by the media like Apple.