Why dont more standalone DACs come with ethernet???

There are definitely getting to be more available. Bel Canto e1X and Black EX DACs both have Ethernet input. Disclosure: we're a Canadian Bel Canto dealer.

Gold Note is another and there are more as well. But, still not very common at all.

Well a stand alone DAC with an Ethernet connection is called a music streamer with a DAC.

The streamer converts packetized internet signal to digital bit stream. This process if done correctly requires a high level of sophistication and a box.... is a stand alone component. The DAC then converts the digital bitstream into a line. Level analog signal that can be amplified in the analog realm. Done correctly it requires high level of sophistication and a box. They can be combined... but usually there are compromises. 

Bricasti seemed to of gotten it right though. Many have said they preferred the internal renderer option to an outboard option. 

How does it sound?
The only important thing to me.

I have a Bricasti M1SE with the ethernet module. After the MDx board upgrade, and in my humble opinion, ethernet is superior to USB.

It seems like there are quite a few DACs with built in ethernet these days: Bricasti, Mytek, PS Audio, Lampizator, Lumin, MSB, Simaudio, Naim, Aurender, Auralic, Krell, Ayre, Hagel, Mola Mola, dCS, and the list goes on.