It's only required for trademarks. Copyrights and patents don't require defending every case to maintain ownership.
Perversely it might actually be a good thing if you did have to for patents as it would force trolls into the open early on (ie before their claims run into the millions).
This is only partially true. You are 'strongly encouraged' to enforce your patent violations, for after a period of years (6) they basically become unenforceable. This is to prevent things like 'patent bombs'.
In practice it doesn't always work this way ( see patent trolls ) but it can be a BIG issue for people looking to enforce their patents.
Perversely it might actually be a good thing if you did have to for patents as it would force trolls into the open early on (ie before their claims run into the millions).