What in the world brought you to such a random conclusion? *laughs*
I dunno exactly, just the way their tribal societies are structured. I was kind of thinking about birds, the way that males have to impress females in order to get them interested, but that's not really the same thing as fertility. And Miqo'te have a reputation for hedonism so it seems like they'd have to have some way of controlling fertility but like everyone else said, there's no doubt natural substances in their world that help do so.
I guess that when I read about the Seeker lore in particular, only the breeding male is allowed to mate with select females, that couldn't be the only time Seekers were having sex.
But yeah, why would "tradition" trump biology? So just me having dumb thoughts.