
Because it doesn't exist, and it should. The lack of widely available network automation tools leads most networks to be built and managed by hand, which means that they're less consistent than they could and should be, which in turn makes them less reliable and harder to troubleshoot.
In the words of our founder, Brent Chapman:
My background is system administration, with a specialization on network design and management. Like many good sysadmins, I'm fundamentally lazy. I enjoy figuring out all the finicky details to make a system or network do what I want, experimenting with the configurations, and figuring out what works best to deliver a reliable and cost-effective service as cheaply and easily as possible. Once I've figured things out for a particular situation, though, I'm not especially fond of the routine, repetitive work that's usually involved in deploying and maintaining what I've designed and built. When it's done by hand, besides being boring, such repetitive configuration work is also very error-prone, which leads to inconsistent configurations, which in turn leads to unreliable services.
Given this fundamental laziness, I've long recognized the power of automation. When it comes to UNIX/Linux hosts, automation systems like Puppet and cfengine give me a great way to turn my designs into repeatable recipes that can be implemented over and over again. There seem to be similar tools in the Windows world, though I'm not as familiar with that space.
However, there haven't been similar tools widely and accessibly available in the networking world. Sure, if you're the average large enterprise and you've got a few hundred thousand dollars to spend, there are commercial packages you can buy. If you've got really unique requirements, and a couple of million dollars to spend, and a couple of years to spend on the project, you can build your own tools. But if you're the typical sysadmin who uses tools like Puppet or cfengine to handle your host configuration and replication needs, what would you use to handle your networking gear (routers, switches, load balancers, firewalls, VPN concentrators, and so forth) and services (Nagios, MRTG, Cricket, etc.)? There just hasn't been any equivalent platform in the networking space, and we aim to change that.
Like many sysadmins, I've often created shell scripts and similar tools to address this problem in a particular situation. These scripts and tools have always been very site- and situation-specific, though, tightly bound to the particular circumstances at hand. Every time I've written something like that, I've wished there was, instead, an easily available platform that I could have built on, as well as a community of users supporting that platform to learn from and share with.
I'm tired of waiting for somebody else to create that platform, and nurture the community around it, so that's what we're going to do.