For the scale at which they operate it probably makes tremendous sense. Although they surely exert a lot of influence on their vendors, they are still beholden

For the scale at which they operate it probably makes tremendous sense. Although they surely exert a lot of influence on their vendors, they are still beholden to those vendors to release patches and features on a timeline they cannot control. This is, IMO, an evolution of the open-source software model. They have a great template to develop/benchmark against, they know what a router in their datacenter should cost, how it should perform, etc. They can create something with the specific features they want and have an immense understanding of a platform that is crucial to their operations. Most likely for much the same reason those chose and open-source model in the first place for their server platforms. There has also been a fair bit of volatility it the router/telecom markets over the years. By owning core technology they are better equipped to maintain their business continuity.