As mentioned before, I don't use a VPN for security.
It does not add any extra encryption on HTTPS traffic, and you should only be using HTTPS anyway. If you are forced to use an unencrypted protocol at any point, yes, you should use a VPN.
It is useful to ensure nobody routing for you knows what sites you are visiting. Except for the VPN provider, who knows exactly where you're going.
It is also very useful to get around content restrictions. Additionally, it's a way of providing secure, authenticated access to internal networks. That is what I use VPNs for most often.