Why did intel not make it backwards compatible? Just to be annoying (as is often the case)?
It's almost never the case, but it might appear that way.
Backward compatibility costs and asking everyone to pay extra for a sound chip when you just need a new driver is unjustifiable. In the DOS days it made sense as a large number of your customers would be unable to use your hardware, but these days it doesn't.
Often the backward compatibility would never be used, because you'd be losing out on new features and who would chose that?
