> on-board sound became good enough You answered it yourself there. Sound hardware started being integrated into the motherboard and/or southbridge/PCH. (Alth

> on-board sound became good enough You answered it yourself there. Sound hardware started being integrated into the motherboard and/or southbridge/PCH. (Although a minor quibble... on-board sound *started existing*. Back in the days of sound cards the only on-board sound would've been a PC Speaker which... well, it can do beeps of various frequencies, but that's about it.) Old sound cards also had various synthesis and MIDI stuff, instead of playing sampled audio, which is great in theory but... then your audio sounds different on every different hardware. Also, these days CPUs are fast enough to do a lot of the synthesis in software (and have extra cores so you're not stealing cycles from something else). That way, even if you really wanted synthesis, not only do you not need extra hardware, it also sounds the same "everywhere".