Nowhere do the Regs dictate in what format the charts and documents should be, simply that they must be current and carried for the flight.
Only because the regs haven't caught up with the technology. Do you really think it's a good idea to blast off with a made-in-china domestic-grade ipad only with no guarantee an app isn't' going to freeze or otherwise disable it, on an IFR flight, with no backup? You're crazy. Battery failure? Did you check that the latest ios update didn't stuff your Ozrunways/Jepp View?
Sure, they work most of the time; so does the aviation-rated gear in my aeroplane that costs hundreds of thousands of dollars to do the same thing, and with which I cannot fly if some go belly-up, despite what I believe to be adequate backup. As I said, some people need a reality check.