You can't have family sharing with app data. If you login into netfilx you are either user A or user B, not a family
They want you to buy 2 apple tv connected to the TV
I don't think Apple wants you to buy multiple ATVs. Why? If a person with two children sees the ATV's $150 price tag, but feels they need to buy one for each family member, they will do the math and decide the ATV is not worth $450 dollars. In this scenario, Apple gets no money. Such a complicated setup actually
detracts from the ATVs value.
If you look at competitors' offerings in this space you will see that the Fire TVs and Rokus of the world also don't have this feature… I don't know why this would be. A lack of multi user support is never mentioned as a mark against these products in a review either. My only guess is that this may be a problem "normals" don't care about.
I think the reason it is absent is simply because of effort. The ATV is
heavily based on iOS, which only supports single users itself. My guess is that they decided the feature would take months of effort and because the competitors don't have it multi user is uneccessary for competing in the market. I disagree with that analysis but I think that is how it went down. Hopefully Apple will introduce multi user support to the iPad (sounds crazy but iOS 9 lets you run two apps at once which was a crazy idea three years ago) and eventually port it to the ATV.
I think it was on a podcast, but I heard somebody say that the Apple Watch was Apple's new hobby. I disagree. The Apple Watch has better design, software support, integration, and marketing. The absence of multi user shows that Apple is content to keep the ATV at parity with its competitors. There are other poorly thought out elements (focus-based UI makes poor use of multitouch, no first party game controller) that lead me to believe Apple's heart still just isn't in the ATV. Or maybe it's part of a larger strategy that will unfold later. Either way what they are launching next month is disappointing considering the three year wait.