From my understanding this is a simple decision: do not focus on something that isn't your core business. Amazon is doing it well, Microsoft is, the cloud is becoming more competitive every day, and they're big enough not to use the public pricing, so it's even more economical for them.
In addition to this, they only need a few "machines" (https://openconnect.netflix.com/hardware/) to have full ISP-local caches of Netflix; why bother with a full datacenter ?
In addition to this, they only need a few "machines" (https://openconnect.netflix.com/hardware/) to have full ISP-local caches of Netflix; why bother with a full datacenter ?