Actor and blackboard arguments redundants in FSM?

This might be a dumb question, but why is the `FSM`'s `actor` also passed as an argument to the `_on_update()`, `_on_enter()`, etc functions?
Couldn't we write the value of the `actor` in the `blackboard` and only pass the later?
It would also be possible for the FSM to leave a reference to itself in its blackboard.

Thanks in advance!