If you are scheduled for an opportunity, the toastmaster can find a replacement. If you are not on the schedule, the toastmaster then knows you will not be available to fill the shoes of someone else who won't be there.
Then there's the matter of being eligible to vote in business meetings.
If it is necessary for a member to be absent from the Club meeting, please notify the Club Secretary, Brenda Daniels DTM, by email in order for the absence to be "excused". This excused absence will not affect the member's voting privileges at Club Business Meetings.