[Earw0rm]

Yep, and not forgetting that serial ports on a computer were (at the time) expensive, and the sounds most synths were capable of were.. kind of simple. So there was the motivation for stacking multiple synths up to produce bigger/richer sound, doing keyboard splits (possible on some hardware of the time but not most), as well as driving many devices from a single port.

Multi timbral synths (different sounds addressable per MIDI channel) were a later thing too, analog polysynths could play more than one voice, but very few could play more than maybe two different _sounds_ at once.