It does happen. For some it is just about the kill, nothing more.
There is a recent (in last two weeks) case out of Kenosha, WI (Olivia Mackay, on the located board) where Olivia was set up to meet a person by an intermediary - it gives the impression of a "date". The three of them went to a beach area and the one guy stood around while the other strangled her for 5 minutes while standing and then held her head under the water for another 5 minutes. Oddly, when it came time to take Olivia out of there the guy who killed her just so happened to have garbage bags in his backpack to put her body in - one up from the feet and another down from the head - before putting her in the trunk. It appears, at least to me, that the killer was motivated (and prepared) just to kill.