What a lot of people don't understand or fail to, Is that it isn't so black and white. Unless there is undeniable proof they VPN you can't just ban them. Because you can actually, to many people's amazement lag and it not be your fault of intentional. There is still places everywhere worldwide (Yes even in the USA) where you can't get wired internet, So you're forced to use Satellite which can be equal to or more than 10x slower(So your 60 MS can become 600 MS) or places like me where ISP's can't route internet to you quickly without interference or it is delivered slower causing a delay. Or the person could just literally have bad internet in general. Should these people really be punished over something they can't control? That's like blaming someone for what race they are. So it's almost impossible unless you monitor that player 24/7 like a hawk to "differentiate legit sparrers" to VPNers.
It isn't that admins CAN'T ban them, It's that when it comes to VPN, It's a gray area with no black and white solution. If you ban one person for sparring because they have lag, Who's to say that they wasn't lagging on purpose? I'm not saying VPN is ok or anything, But it you want them banned or something you should work with an admin about it, Contact and PM one in game and talk to them about the player, Don't use screenshots as they are not considered valid proof.