Deleting expired events.

That is correct.

The idea behind Event Rocket’s cleanup tools is to purge the database of nearly all event related data, including settings.

The use case is for users who have decided either to abandon The Events Calendar (and so want an easy way of de-cluttering their database) or for those who are sticking with it but need a clean start (perhaps because they’re resurrecting an outdated website having upgraded from a much older version of The Events Calendar, or something of that order).

I did previously make a plugin called The Events Calendar Housekeeper available, the purpose of which was to manage expired events – cleaning them up after a configurable interval of time had passed – but a lack of time and significant changes in the codebase for The Events Calendar (and Events Calendar PRO) meant I was unable to keep that going.

At this time, I think the best course of action if you want to see this sort of functionality is to request it be baked into The Events Calendar itself.