The point about these 2TB is, as OWC says: "performance and capacity" - uncompromisingly. These drives are made for people who need the performance. And I'm sure many of the targeted audience will count on consistent performance. It's a premium product for a specific audience, to be put in High-End machines, where price is secondary.
Hybrid drives on the other hand aren't "uncompromisingly fast" - they aren't faster than conventional hard drives in Reads once you hit the "wrong" sectors on the drive. And for demanding users/uses, many Writes won't be either. Hybrid drives don't achieve consistent performance, so they are no substitute for SSDs.
Also, keep in mind that hybrid aren't only inherently more complex from a design standpoint (you'd not only have to get the SSD part right but also the communication and caching between SSD and conventional drive), they should also be less manufacturers being able to produce them. Conventional hard drives have to be assembled in a cleanroom environment (and I doubt you can get them "barebones"), while SSD should be easier to assemble.
For companies, it's not only much easier to get into the SSD business than the one for conventional HD - the former is a burgeoning market while the latter is shrinking.
Bottom line: Hybrid drives give up the benefits of proper SSD (uncompromising and consistent performance), are more difficult to design, test and manufacture (especially companies that don't already make HD), the targeted audience is small (esp. in the Apple world, it'd only fit in Mac Pro and iMac 27", nothing else) and the advantage compared to existing 2.5" hybrid drives is only a relative one (no way near as significant as to SSD).
But why don't go and purchase an SSD and create your own Fusion Drive with Disk Utility? There are instructions on how to do it...