Infertility is a common feature in "Sertoli cell only" syndrome because -
Sertoli cell only' syndrome is another name for Germ cell aplasia.
In this condition, seminiferous tubules are smaller than normal and are lined by a single layer of Sertoli cells. There are no germ cells lining the seminiferous tubules.
Absence of germ cells leads to absence of spermatogenesis because spermatogenesis begins from primitive germ cells, leading to infertility
Too many Sertoli cells inhibit spermatogenesis via inhibin
Proper blood-testis barrier is not established
There is no germ cells in this condition
Sufficient numbers of spermatozoa are not produced