Geographical IP relocation seems like a common reason to use it. Also just because Google may have access to some information it doesn't mean that everyone else has.
You can't stop companies from gathering information when you interact with their services but you can do things to avoid having all that information aggregated (it would require using different IP addresses for different services, so a VPN can help, among other things).
Some public networks (like those at airports and coffee shops) still do sketchy things like injecting ads into HTTP sites and breaking DNS. A VPN is a great solution to these problems.
