probably because nobody likes to use Hulu and suffer through commercials.
I only have Hulu now, because they gave me a full year of it for $12 on cyber Monday last year.
the companionship with D+ may make me contemplate another year, but literally the only things I've watching on Hulu since having it is the most recent season of AoS and the second series of Naruto (my daughter was obsessed, so I started watching it with her - first 5 seasons of series 1 was on Netflix though)
If they come up with a decent bundle deal, I may extend my Hulu subscription, but chances are, as long as they have commercials, and I can find it streaming elsewhere.... I will watch it elsewhere.