Because not all apps that will run on Maemo 5 will be Maemo apps. By using the stylus and resistive screen, they can use desktop Linux apps as well, without needing to redo the UI for touch. The iPhone is limited in this regard, and mostly by its screen. Its a small feature many overlook, but the geeks and technofiles will appreciate it. They made it good enough where I don't see how it matters so much. You have the best of both worlds.