They're stuck in a local optimum. These companies have to be structured in a certain way to succeed at low margin, high volume commodity hardware sales. It isn't easy to adapt that to higher-end products, and when they try the market is slow to recognize changes in a brand, which discourages them from trying.
R&D spending: when you are in a race to the bottom, you can only afford to invest in safe designs, and most of your focus is on efficiency. In contrast, Apple can afford lots of R&D spending.