It's basically a non-standard use of IPv6, which is to ideally issue a /64 to each end point. Personally I don't mind, but some people think they need 18,446,744,073,709,551,616 addresses per host.

The idea being with all those addresses you can create subrouters to manage your network topology. Unless you're doing some weird tunnelling setup through your VPS, I can't see why you'd need or want such a huge block.

People complain about only getting a /64 on their home routers.

Blocking certain outbound traffic is another matter: that really stinks.