Probably because they got rid of it when the XT came out, so it was only there for (a few months under) 2 years. But it was a good trade; removing the cassette port gave enough area on the PCB for 3 more ISA slots.

Way, way back when, you were lucky to get a serial port built in to the motherboard. everything was an add-in card. But you did get a tape drive interface. It was just an audio jack you plugged into any cassette player. You had to start and stop the tape yourself, of course.

It's funny how close an early PC was to the 8-bit machines: you had BASIC in ROM and a cassette interface.

You could even use a TV!

Those aren't rare on 16-bit or less, '80s and before, pre-MS-DOS home computers. Looks cool, but apparently it was way too slow and painful to be fondly remembered.