Does a VPN do Anything to Protect You?

With the predominance of Deep Packet Inspection (DPI) on networks, I wonder if the NSA has been using DPI all along to intercept our data traffic at the 8 primary internet hubs? Does a VPN even matter considering that the major Internet Service Providers (ISPs) route all of our traffic? My guess is that the NSA sends all traffic for inspection prior to sending it on to the VPN and other providers.