One reason is there already was exabgp, written in Python, which in my experience is slow and resource hungry. Golang is much faster, easily portable, and produces static binaries (easy to deploy).
Another thing is bgpipe speaks JSON to background (or even remote) packet processors, so basically you can use whatever language you want with it to drive your BGP routers.
Another thing is bgpipe speaks JSON to background (or even remote) packet processors, so basically you can use whatever language you want with it to drive your BGP routers.