Yes, it's the cheap DACs and streamers that have really been pushing I2S. It's a shame people are basing their choice on a connection with no universal standard
Ben of Mojo Audio has stated more than once that I2S is not his preferred scheme. An excerpt from their site
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I2S was engineered as an internal transfer protocol for inside of DACs and ADCs and is the language most DAC chips read. In most DACs all other transfer protocols are converted to I2S before they can be sent to the DAC chip. The official specification for I2S is that it should not be used for longer than 4”. This is why so few companies sell I2S compatible CD transports or DACs: it is not necessarily a good idea.
Think about it: all other transfer protocols are a bit stream with embedded clocking. Companies who boast about the performance of their I2S claim that the clocking in a single bit stream becomes corrupted. You see I2S has three wires: the data stream with embedded clocking, a bit clock which synchronizes with each bit, and a word clock which synchronizes with each digital word. If clocking in data streams can get corrupted, then why would it make sense to try to synchronize three data streams and clocks?
The only reason I2S sounds better on a specific DAC is because the other transfer protocols are of a lower level of performance. In a sense I2S saves the manufacturer money in that they are relying on expensive clocking from the component feeding their DAC rather than integrating such high-performance clocking.
So, which transfer protocol has the best sound? That would depend on the digital source (server, streamer, or CD transport), and the quality of the specific digital input on a specific DAC. Most DACs don’t have the same performance from all their inputs. Many DAC manufacturers will even state their best input is USB or Ethernet or S/PDIF. And even if you have the best input on your DAC, if you’re using a less than optimal digital source, overall performance won’t be all that good. So, once again, transfer protocols are not universal, but highly component dependent."