They're a company that wants to stay in business. TV's about as locked in as can be and even they're draining audiences in one form or another. The internet is an amazing levelling field, and even if terrestrial TV packed up and quit tomorrow, there'd be no firm reason NetFlix alone would dominate the internet markets. They're playing the same game by locking up good content behuind their platform so that if/when the sh hits the fan, they'll have something to keep loyal customers paying well for their services.
I might phrase it differently as adapting to the eventual market.
Netflix isn't going to be the only big web distributor for long. Not only are cable companies putting out their own distribution networks but so are the Networks who produce content. When there's 10 services available people are going to go to the service with the hit shows, if each service is also a content provider they can create the exclusive hit show that preserves part of the audience, if not they wither away and die as their audience is slowly siphoned away.
If Netflix wants to survive they need to produce a show so they can control the distribution. Hopefully this leads to cross licensing so you can watch everything by choosing among competing services, but even if not a fragmented market is better than a monopoly.