Desktops are still made from interchangeable components. I upgraded RAM, video card, sound card, added more hard drives, retired old ones. Later on I replaced

Desktops are still made from interchangeable components. I upgraded RAM, video card, sound card, added more hard drives, retired old ones. Later on I replaced CPU+motherboard (unfortunately you can rarely just upgrade the CPU). If you're not lazy, this can save you quite a lot of money. Phones are nothing like PCs, and will not be for a long time. It would take some crazy engineering to make them lego-like, or even plain upgradeable.