Some of us are different from you. 🙂 All I can get is very slow Verizon DSL in my rural location. Streaming perfromance is poor, even in standard definition. I have plenty of disk space on my iTunes server and want to have all my content stored locally.
I'm pretty sure you're wrong about AppleTV support for local extras. IIRC, they made them available with a firmware update on the AppleTV 3, however only the extras that were included in HD movies and not SD. Regardless, this is just some kind of marketing thing from Apple IMO. It surely wouldn't be hard for them to make any version of the AppleTV compatible with locally stored extras. For some reason, they just didn't want to do that. IMO, their whole direction has been away from local iTunes libraries. They would prefer for you to be totally dependent on their own servers, where they can control everything. But "it is what it is"…
And I actually enjoy watching the extras repeatedly over the years, provided that they are of decent quality. Watching a documentary beforehand generally enhances my enjoyment of the movie. Most of my library was ripped from DVD, and if the DVD extras are decent I also rip them and put them in the "documentary" genre.