Is there a reason we have to offer 2 or more ships within a fandom?

There is a fandom I'm interested in writing for. Three of the four nominated relationships are out of my comfort zone, but here is one that I'd really like to write. Since it's already possible to nominate a fandom with just one pairing (so presumably there will be lots of offers with just one pairing in the offer), wouldn't it make sense to allow any offers to have only one pairing?

Thanks!