...and having a TOSLINK port in addition to HDMI would inconvenience people how, exactly? It's not like it would cost you more: this is Apple, they're charging as much as they think they can get away with for a given product type, not some narrow margin on top of the bill of materials.
There is plenty of perfectly good equipment out there that does have TOSLink, and even more that can be connected via a cheap TOSLink-to-phono converter. As I said, I don't want TOSLink to connect to my TV, I want any aux audio output for when I'm using the ATV to play music. You know: stereo. music. To play over my nice old fangled stereo speakers (preferably without having to turn the TV on). That was mixed by folks in the 70s and 80s to sound good on stereo speakers. That I don't want processed into pseudo-5.1. (which can be fun, but not always what I want).
I got an ATV 4K because I might get tempted to buy a new 4k TV and soundbar over the next few years as more stuff comes out in 4k - not because I want to chuck my existing kit on a landfill today.