Why?
People (vampires or humans) are still behaving kind of weird. Animals suffer if their partners die - humans (and vampires - who live way longer) suffer way stronger compared to most animals (elephants and apes - surely some other "higher intellect" animals are also suffering more than others).
So suicidal thoughts will be common amongst the prisoners and vampires based on loosing partners, being unhappy for rejected love, for whatever reason ....
Laying the fate of the whole planet into each individuals hands ... will so lead to issues.
Dunno what is "quite odd in response to mine" there? You wanted to create a quandary (need to use the word I just learned two weeks ago

) - but it fails here as decisions cannot be done strictly based on the rules you created.
bye
Ron