Why does USB feature so much in discussions about DACs when the newer HDMI seems better?

My take: Audio Video HDMI is only available within the video world.  BluRay players that can play SACDs works only with Home Theater receivers that can decode DSD. I only have experience with SAME BRANDED BluRay and HT Receivers. Not sure how well it works with mixing brands.

To make it more confusing, then there are SACD players that use HDMI (that is I2S, but uses HDMI cables, no video involved) that can be connected to external DSD capable DAC using I2S via HDMI cable.  It can be a bit complicated as I2S pin outs are NOT standardized. So caveat emptor

I2S was designed for audio. Toslink was a cheap way to send digital signals developed by Toshiba. USB was for data not audio. When you look at it from a cost and convenience factor and take into consideration what technology was available at the time, one can see higher end audio components are using I2S because it’s better engineering and better sound today. Of course anyone is free to use whatever connector that might have and if it sounds fine for them…. no worries. Paul McGowan of PS Audio explains these differences pretty well in his informative YouTube videos.

Navigating the depths of digital ignorance calls for a strong submarine.

@2psyop   Thanks to you, I am enjoying Paul McGowan on YouTube.  Straight to the point and authoritative.  I particularly like his comparison between DSD and PCM - probably because his assessment and mine agree!

My understanding is that I2S is a two-channel Pulse Code Modulated interface designed by Philips to connect integrated circuits on a board, and dates way back to 1986. There is no agreed cabling standard.

For those who believe that USB covers a lot of audio standards, here is an extract from Wikipedia on HDMI audio:

"If an HDMI device has audio, it is required to implement the baseline format: stereo (uncompressed) PCM. Other formats are optional, with HDMI allowing up to 8 channels of uncompressed audio at sample sizes of 16 bits, 20 bits, or 24 bits, with sample rates of 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, or 192 kHz.^[5]: §7 HDMI also carries any IEC 61937-compliant compressed audio stream, such as Dolby Digital and DTS, and up to 8 channels of one-bit DSD audio (used on Super Audio CDs) at rates up to four times that of Super Audio CD.^[5]: §7 With version 1.3, HDMI allows lossless compressed audio streams Dolby TrueHD and DTS-HD Master Audio.^[5]: §7 "

I'd just add that Dolby Atmos is supported, with up to 32 channels.  There is a licencing cost for HDMI which may put smaller manufacturers off using it.  There is also great confusion over the theoretical capabilities each version of HDMI specifies, and the actual capabilities that are implemented by the component manufacturer.  They are supposed to list the actual capabilities, which as @devinplombier says, plumbs "the depths of digital igorance" for consumers

@rbstehno what is wrong with USB? Is external hard drive losing bits?