Do I understand correctly? You use WireGuard to set up your own VPN servers? Doing this is a lot more expensive than buying a VPN subscription, but it can be more secure if you know what you're doing, right?
'Buying a VPN subscription' is just one use-case. Usually, those VPN services are intended to be used to circumvent geo restrictions.
WireGuard is not only about that. Sure you could do it. But it is applicable for any use-case where you have two or more machines that need to talk over a secure tunnel, over an otherwise not proven to be secure network(which is usually, but not always, the Internet). This ranges from connecting to a machine you have at home, to exchanging data between two office branches, and so on.
A VPN is one use of a Wireguard tunnel. Wireguard establishes a stateless encrypted connection between two peers, and exposes it to the user as a network interface. Endpoints can roam as with mosh
WireGuard is not only about that. Sure you could do it. But it is applicable for any use-case where you have two or more machines that need to talk over a secure tunnel, over an otherwise not proven to be secure network(which is usually, but not always, the Internet). This ranges from connecting to a machine you have at home, to exchanging data between two office branches, and so on.