It really comes down to him being the only one worth it in Selene's opinion, both for him and proving her conviction to his father.
Other than that I think the bulk of the bodies would just have had full on sustained bites (complete with venom/drool) from the Lycans and therefore the dreaded "bite from both species" that kills even one of them.
We don't actually know what kind of Corvinus strain she has, probably a unique one altogether, that would not be "pure" and still retain Vampire traits that would make it impossible to bring back one of the Vampires with the Lycan virus in their blood too. Or worse, reanimate them in horrible agony as though their blood was burning.