It's very hard to make them perfectly recyclable because of how the materials are used, to begin with. A computer is the most cutting edge device you have in your house, with very sensitive parts that need to fulfill a wide array of tasks, and thus need a series of different parts that each require different materials. Even if you only take one component into consideration, there are still several subcomponents in there that need different materials to fulfill their roles. And the more different materials you need, the harder it is to recycle.