They didn't get used much because software support was not there. There were issues with Windows 95 and NT4. But also many PCs would stop at POST without a PS/2

They didn't get used much because software support was not there. There were issues with Windows 95 and NT4. But also many PCs would stop at POST without a PS/2 keyboard plugged in. But new PCs had USB ports before the software was ready, for about a year or so.