These were working girls. They weren't out there looking for a boyfriend, they provided services for money. I'm sure being a semi-normal guy that wasn't a total weirdo helps, but that's about all that should be necessary. Didn't the killer phone ALC several times the day she was last seen alive before she left to meet up with the guy? There's been a lot of talk that he doesn't kill every girl he comes across, just when the urge strikes. This was also the case with Joel Rifkin.
We have to be careful jumping to the conclusion that the guy who spent a lot of time on the phone with ALC, promising her a lot of money, and insisting she not bring her phone (and recall, she left as-is, jeans and a hoodie) is the Killer. Granted, it looks very very bad for him. But we don't see any such nefarious methods in the cases of the other three girls. I have a hard time reconciling that MO of an apparently bad-guy john, with, for example the way MBB disappeared from a Bus Terminal. Seems like entirely different types of behaviour. And yet, they both ended up dumped on the side of the expressway with MW and MB. It is almost as if all we really have is four girls who were engaged in the same business, each of whom advertized on CL, ultimately ending up in a common dump site.
AstroKitty is evidently aware of the type of behaviour exhibited by the ego driven john as described by DS. AstroKitty, did those bad-guy johns end up killing their "prey"?