I understand it's probably because the GPS functionality is integrated into the same RF chipset that's handling wifi/bluetooth, but it would be possible to make a "no transmit capability" camera that still has GPS metadata functionality, with GPS receiver chip and an antenna tuned for 1400-1600 MHz, since ordinary consumer grade GPS is a receive-only technology.

But that would still possibly present a problem for serious government use where it can't have an antenna of any form in it.