And actually there ARE photographers who specialize in same sex ceremonies. I don't know if any have been approached about a traditional service (opposite sex couple at a "conservative" church).
An article I saw in a photography publication highlighted some of the differences between photographing a traditional wedding and one with a same sex couple. Some of the standard/stock poses don't work if both are wearing suits (garter, etc.). Often the extended family (who would pose around the couple) don't attend (because they are "discriminating" by not attending).
It is called the porn industry.