The thing is, Cakewalk really isn't a hardware company. So even if you purchased an interface through CW, that hardware wasn't created or supported by them. I guess it's sort of like purchasing a third-party app through the CW website - the location of the purchase isn't really the key factor when it comes to support.
Plus, I'd imagine the drivers would work in a similar fashion with any DAW/OS combination. For example, say a user has a CW/Roland interface running on Win7 with Cubase. Cubase updates to Win8 but no drivers for the interface. Wouldn't Roland be on the hook? That's why it makes sense (IMHO) that Roland is the key in this instance - they have to support the interface on specific OS' regardless of the DAW being used.