FreeBSD may have less then 1% of server market share but FreeBSD drives a large amount of network traffic. For example FreeBSD runs the open connect CDN that Netflix uses and that accounts for almost 32% of North American downstream traffic [1]. Limelights edge CDN nodes run FreeBSD and Limelight is one of the Bigger CDN companies out there [2]. Juniper routers are FreeBSD based and are the second most used routers after Cisco. There's plenty of other examples but FreeBSD may not be widely deployed but it serves a significant amount of the worlds internet traffic.

[1]: http://testinternetspeed.org/blog/half-of-all-internet-traff...

[2]: https://www.freebsdfoundation.org/testimonial/limelight-netw...

[3]: https://en.wikipedia.org/wiki/Junos_OS