What need seems so obvious to me that can Not Imagine search engines can NOT FIND even a discussion on Why it is Not available.
My gran-daughter was wanting a way to get 'instant' pictures like the old Polaroid. (The cost of film is ridiculous!) Found a portable 4x6 photo printer at a thrift shop. When first tried to make it work found that the USB port Is-NOT. Something called PictBridge ONLY.
Yes she can use an SD card to transfer pictures from the computer. Technologically it must be possible to have a program for the computer to 'emulate' a PictBridge camera; use these printers directly.
No search has found that to be possible. Hopefully someone reading this forum has heard of this being possible and can point me toward that solution.