The type of repair isn't really part of the Apache Cassandra repair paradigm at all. When it was discovered that a read repair will trigger 100% of the time when a query is run at ALL consistency, this method of repair started to gain popularity in the community. In some cases, this method of forcing data consistency provided better results than normal, scheduled repairs.
Let's assume, for a second, that an application team is having a hard time logging into a node in a new data center. You try to cqlsh out to these nodes, and notice that you are also experiencing intermittent failures, leading you to suspect that the system_auth tables might be missing a replica or two. On one node you do manage ...
