You could have a contagious disease without a fever. Your loved one could be in the hospital- or is the fever or fracture of someone else a valid reason? 3 F's makes a great soundbite, but really, a person should be reasonable and accept other excuses to miss a meeting:
work
The only free time for some important event or scheduled meeting with someone else
Kids need to study/rest for a big test that will effect their grade and future
vacation
It was just too nice out to sit in a Kingdom Hall
The release of the next Star Wars movie (or whatever movie you fancy)
Just tired