We wanted our stuff to charge faster. We can't pull more amps through the thin USB cable wires and contacts without turning them into detonation cord, so we increase the voltage instead, and due to Ohm's Law, we get more wattage out of it as a result, so now we can charge your phone in 20 minutes instead of 3 hours. And because some devices can take advantage of this, and some can't, we had to build some logic into the power delivery system to avoid frying things.