There are plenty of soundcards with 4 or 8 line inputs and no preamps. This gives you a computer interface that you can use with a mixer, and use your computer like a multitrack tape recorder. Mic preamps up the ante so that anyone who isn't that serious about recording and isn't likely to pop for a $1000+ mixer but wants to record with a mic can do so with minimal gear. But of course adding mic preamps increases the cost and it's likely there has to be a compromise to fit preamp circuitry in the same box as the converters. The OMNI i/o is really an add-on to the Delta 66 card that allows people that don't have mixers to be able to record with mics, but it's meant to be small and low-cost, so there's only two preamps and one headphone out.