That still doesn’t answer why TMI doesn’t support followers. If you’d rather use the API, fine, but I don’t see why that choice should be the limiting factor. If TMI is inconvenient to Twitch, I don’t see why they’d keep it around.
I don’t want to develop software that has to run on both APIs if it doesn’t need to, it just seems rather silly that Twitch would implement so much functionality into TMI, but skip follower support and point people to the API. I don’t need the last 25 followers, I need them as they come, and I already use TMI in my bot.
There’s no real reason I can see to not trigger a follower event on a service that Twitch has already implemented and supports, and that most streamers already use. If TMI is buggy, that’s not a reason to not trigger a follower event, it just means Twitch has some work to do with TMI.