I'm not sure you're right, or at least as of late Supermicro has been selling X[9/10]SAE workstation motherboards, which will take a Xeon or consumer chip and ECC/non-ECC memory. No IPMI, lots of the sorts of slots we want, and onboard sound. The first X9SAE model, with which this message is being drafted, would appear to have been successful enough they repeated it in the next generation:

http://www.supermicro.com/products/motherboard/Xeon/C216/X9S...

http://www.supermicro.com/products/motherboard/Xeon/C220/X10...

They didn't make such a class of boards in the '8' generation.

Not dead yet!