This AR method does more harm than good, especially in large codebases.
https://github.com/rubocop-hq/rubocop-rails/issues/76 lists these
bits of evidence against it:

* https://rails-bestpractices.com/posts/2013/06/15/default_scope-is-evil/
* https://andycroll.com/ruby/dont-use-default-scope/
* https://stackoverflow.com/questions/25087336/why-is-using-the-rails-default-scope-often-recommend-against/