I agree entirely.
My answer is the expected answer from Twitch towers.
I actually expect Twitch to have more people on mobile or console at the moment [citation needed], or at least the largest growth area (and hey lets not even get into the second screen argument), rather than being a user who uses the non default interface. Of course that is my opinion.
My opinion is also based on any of the additional internal lookup that is required by Twitch in order to serve any of the suggested additional tags, we’ve got bandwidth increase both internally for the lookups and bandwidth increase just to serve these additional tags, and as @3ventic points out, who knows how much Emote tag data is or is not going to be attributed to a tag that may/may not violate the RFC for the length of tags (which granted Twitch doesn’t care too much for the RFC’s), and yes I suppose these extra tags is just marginal compared to the possible Emote data.
I’m not adverse to this extra data, but considering the whole system as a whole I wouldn’t expect it to be added, and most of it can be cached/generated via the API and done with as you will in your own systems, potentially more efficiently than to have your IRC/Tag parser have to parse the extra tags out for every single message sent by Twitch chat…
Of course this would naturally be under a “tags-extended” cap, so only those who want it can consume it.
I apologize to @moocat for appearing stupid, I just didn’t expand my initial answer. But as a systems engineer, I consider bare metal to end user and see the whole system model.