As we have already seen, it's very important to encrypt everything, and even more if your traffic passes through third parties or shared networks. Since you might need to connect some external resources (such as servers in a remote location or your laptop to do some configuration) to your tenant network, OpenStack Networking allows you to create VPN end points in a few clicks or commands.
This is very useful if you use some unsafe protocols. If you will use only safe protocols such as SSH and HTTPS, you can still use a VPN if you want to be sure that no one will be able to even collect metadata of your communications.