Scrum Events Facilitation/Lead
If we think at the Sprint Retrospective, Planning, Review and Product Backlog Refinement,
would there be a Scrum "accountability" ("role") who is going to lead and facilitate these events?
If there is a need to do so -- or if it has been requested -- then a Scrum Master may provide such a service. There are a number of stances of this nature which may be adopted at various times.
He or she would also take care not to become a dependency or constraint. A Scrum Master is not a master of ceremonies.
Going to start with pointing out that Product Backlog Refinement is not an event, it is an ongoing activity. Given you feel it is an event, I suggest that you re-read the Scrum Guide to refresh your understanding of the framework.
Each event has a unique purpose, why would a single individual/role be held accountable for this? When a team is self-organizing and self-managing, the teams should decide how best to structure the events and activities. Remember that some of these events and activities are ones where the Scrum Master is also a participant. So in terms of "facilitation" it is best to have a non-interested party help with facilitation.