I don't know how much this is a factor, but...

Amateur-level choirs tend to have a lot more basses than tenors because it is easier to sing bass without effort spent on vocal training.

FTA:

> When men do join singing groups, they often avoid the tenor section. The tenor voice is “a cultivated sound”, says John Potter, author of a book on the subject. A man with no vocal training is more likely to have the range of a baritone (a high bass). It does not help that the tenor voice is associated with operatic stars such as Luciano Pavarotti, who could powerfully sing high notes that no amateur can easily reach. And the tenor line in classical choral music can be difficult, with many unexpected notes and alarming leaps.