Cartridges were used in Consoles (Fairlight, Saba).
Cartridges were also used by Computers like MSX, Atari 400 etc.

Tapes comes from the mainframe tapes and were popularised by music too. so often people used normal tapes-drives and for a zx81-games - there were even description how you had to connect the microphone-cable to the head-phone-jack and reverse. While loadibg a zx-81 game you hear the whole time the data coming in! so meta: sound was for people and maschines.analog digital. So there was no difference between an accoustic coppler and data from the tape. 

sending information via snail mail on disks