Good points. QTM is a storage product company as you say. They make the tape libraries and DXi disk systems to copy your data from your primary storage to secondary storage is the way to put it I guess. I don't see QTM as a primary storage company like NTAP, IBM, EMC, etc.
Yes, you could make a DXi out of a pure flash array. But it would be really expensive and their customers don't need that kind of performance yet. And aren't willing to pay for it. No sense building something you can't get customers to buy.