There are a few physical buttons for the few critical functions you might want to trigger in the boost/reentry phase. The rest is either 1 g or microgravity and a touchscreen should not be a problem.

BTW, not surre if they implemented it in the end, but they planned to handle screen blurring due to vibrations by shifting the screen content based on accelerometer data in real time. A rather clever idea IMHO. :)