OpenSebJ - Realtime Audio Sample Mixing

It would be nice if OpenSebJ could record by streaming it's output directly
to a wav file bypassing the soundcard altogether. The only problem with
using the soundcards internal wave feature is that there's a digital to
analog and then back to digital conversion which means loss of quality.
I've always wondered why all soundcards do it this way. There's no reason
why this shouldn't be a completely digital process.