I was thinking that I would actually have to add a reason to your list.
Reason 6: Because sex is a fun and fascinating activity.
Sometimes you want to go fishing just because you like fishing, not because you're hungry for fish. This is the part of my drive which occasionally makes me think I should just get a "fishing buddy" and stop pestering my H so much.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver