For any creator/organization willing to enable this, stale pull requests will have a good reason. eg it was started by a person who is no longer actively working on the project. Having a few stale PRs isn't a big deal.
Is there a specific reason this was created? Git-enforcer has only 12 total (closed) PRs and the default max open PRs is 10.
This is a tenancy of the agile methodology to have some sort of WIP, so we tried it out as an experiment and it greatly improved pushing PRs through to master.