Vampires, if written consistently, are too selfish for true friendship, anything that looks like friendship is motivated by the assumption that this person can do something for me. Affection can never be internalized. Pick your random Internet pop psych diagnosis, narccism, sociopathy, psychopathy and go with that
making you laugh/being pleasant company is doing something for you
Also, with this idea why would a vampire ever feel enough about a person to turn them besides wanting lackeys?