AFAIK homosexuality is not an inherited trait but a genetic malfunction, pretty much the same as colour blindness, unexpectedly tall, short or chromosome accidents [down syndrome, PWS, etc].
Even if it were an inherited trait it would still not be advantageous to the group to have one non breeding member. As a rule gregarious animals limit their offspring to a number that can easily be supported by the group. Normally this limits the breeding to less than is possible. If something was to happen to the alpha members, it is essential that these be replaced as soon as possible to continue the species. If one or more of the tribe were non breeding it would limit the genetic diversity of the group to an undesirable level.