Those require a power supply. A usb miner would definitely be more appealing for beginners/hobbyists.
Frankly, beginners/hobbyists are just wasting their time if they're messing around with miners at this point. Of course, a market may exist for such a novelty item nonetheless, but...
The fact that thousands of 333 Mhs USB miners still change hands on ebay each month should indicate that there is a large demand for usb miners.