Not understanding how Hulu+ works...

Why is it that when I browse Hulu+ on a computer, EVERY episode and season of a show is available to me. Yet, when I try to browse Hulu+ on my Roku, Apple TV, etc... the selection is very limited.

Is there any reason for this? Doesnt that ruin the whole point of Hulu+ on non-computers?

I suppose I can simply Airplay Hulu+ from my Macbook onto the Apple TV, but that isn't the point.