I've had a lot of problems with Norton VPN. Often have to chat - download - uninstall - reinstall - blah, blah. When I talk to support they "fix" the problem, but never seems to stay fixed. Norton should never have released a VPN - and now they should make it an optional ad-on. It has been and still is a piece of crap.
What error messages are you seeing with the VPN?
As for it being optional, it technically is optional. It will not turn on unless you manually turn it on. If you do not want it, do not turn it on.