However much current you can draw over your USB socket, it's still only 5V. Many devices want a (far) higher voltage than that for charging or powering themselves. A quick glance at my laptop PSU shows 20V, presumably related to the voltage of several Lithium Ion cells in series.
Yes, a given psu could transform the voltage back up with switchmode, but then you've got the horrible transformation inefficiency twice!
I wonder how many devices there are out there that actually want that much current at 5V.
Yes, a given psu could transform the voltage back up with switchmode, but then you've got the horrible transformation inefficiency twice! I wonder how many devices there are out there that actually want that much current at 5V.