As people age they start losing some of their high notes. So Senior Choirs often have to be pitched down 3-4 steps.
In our small choir our Tenors, who have been doing melody, are just starting to reach up to their parts. They are all 50+. One "Tenorette" woman, and 2 older men, a Baritone who can sing up to about Eb-F and the other who sings into the Alto range.