Could be for any number of reasons. Take your pick:
- The shows themselves are not recorded or available in surround sound- Netflix itself may have issues. Like late last year when it pulled surround sound from Samsung smart TVs and Bluray players because it just wasn't working.
- Hardware limitations - as in does the device support surround sound or do you have a receiver that actually supports it correctly.
- Software limitations
Since I don't have a receiver, when you guys are watching a title that actually has 5.1 sound, when you go into sound / subtitle options what choices do you see? (assuming you have something connected that properly does 5.1 that is not your TV)
Hardware or software limitations cover a huge range of issues. They are correct assumptions as a result.
Bandwidth will not be the issue. Audio can be easily compressed and uses much less data than a HD video stream. That and the Netflix app is currently capped at 720p.
Changes to apps on Optik TV boxes will take time. I'd assume you'd rather have 1080p video to go with your 5.1, yes? That will add more time, and a lot of testing before it's all released to the public. Estimate a couple months minimum for that process based on previous update cycles for STB apps.