Is there difference in performance?
iirc it is because it needs to support plugins and this only works with CGO. Also, using openssl implementation for some crypto stuff is more performant.
We don’t ship with openssl by default, you need to build from source for that.
It is indeed for plugin as well as libnss for name resolutions.
This make your binary very slightly smaller when you first start, you probably can’t mesure this on Kubo.