If you are a professional pool player, you can buy two or more shafts of various sizes amd makes for various purposes. Otherwise, one shaft is sufficient.
One shaft is not sufficient for a professional. I can guarantee that if you surveyed 100 pros, 163 would say they do not and would not choose to play events without a a backup shaft.
How did you form your opinion?

Woul you opine that one does not need a spare tire in his vehicle's trunk.