Oh, quite possibly. I'm sure there is a good reason. I guess I'm just looking at it from the view of the giftee rather than the creator. Not everyone has 5 Snape pairings they like. I mean I can write Snape/almost anyone but for a gift for myself? I'd really prefer maybe 2-3 pairings. *shrugs*
Or if the author/artist is versatile enough to choose from any of 5 pairings, I am not sure that really means they would ONLY be able to write slash or only het. From what I've seen the authors that write the most different pairings write slash/het/gen.