Why DACs have no BNC Digital In

@op, The reason why BNC is superior depends on the connector impedance...its hard to make a 75ohm rca cable.
http://www.nagysaudio.com/digitalcabletech.html

A good read.

Hopefully dac manufacturers use it on the future?

The original Benchmark DAC1 has a BNC input.

Chicken and egg story all over again. Which came first? In this case it was CD players and transports. If very few have BNC outputs then DAC builders don't see any need to include a BNC input.

I am not arguing which interfaces are better just that there are so many digital interfaces those that were not common became even less common.

Interface connectors I can think of: RCA, AES/EBU (XLR-style connectors, USB, Toslink, Glass fiber but not Toslink (ATT?), i2S, BNC.

I would not purchase a DAC that does not have a BNC input.

The two DACs I have owned in recent years -- the PS Audio Perfect Wave and the Northstar 192 -- both have BNC inputs. I always assumed those BNC inputs were included because BNC digital outs are more common on European transports than they are on US transports. For most digital transports made for the US market, the only outputs I ever run across are S/PDIF and Optical.

I have tried connecting my digital transport, the Perfect Wave Transport, to my Perfect Wave DAC using a BNC and an RCA digital cable. The two digital cables were from the same manufacturer. I could not tell any difference in sound quality between BNC and RCA.