"...they risk turning into a dumb pipe".

That's their problem, they don't own the pipes either. They don't own the pipes and they don't own the content (before House of Cards). Up to now they provided...well...a useful cute little UI, but it's hard to make a lot of profit for a prolonged period of time on that. So they either go into pipe building or content building. Content building has the better leverage to the large customer base they've got, and in that context producing House of Cards makes perfect sense. I hopes it works out for them.