Why the elaborate process with the seduction, taking to secluded areas where they can be transported to another dimension or whatever was happening there? And why only men? Seems like a plot-hole just to get a story about a woman seducing men. Otherwise a species with the technology to travel between star systems could just pick up any humans anywhere without this faux seducation racket.
We know almost nothing about the being that we see seducing men. This might be the way it preys on its food supplies, perhaps not limited to humans, like a spider. It might also be something that this creature enjoys doing; for all we know, it's considered a psychopath where it comes from and this behaviour is aberrant.
Obviously, the movie suggests strongly that this is a hunter-prey scenario and the being is using its form to create vulnerable people whom it feeds on. That feeding process, however, is also ambiguous, and we don't know what is required and what isn't.
There is something obvious, however: men are easy targets for a hot babe. I've heard that they used hidden cameras and filmed Scarlett talking random guys into getting in the van and then later asked them to sign release forms. So, this is obviously a credible way to lure in prey. Why lure them? Can't just kill out in the open.
The bottom line is that we can't take it for granted that this is an unnecessary elaborate process, because the *requirements* and exact nature of the creature doing the stalking is unknown or ambiguous.
Men have more meat on them and can be harvested more often without the food population taking a dive. It's like hunting Bucks for a constant supply of meat and sparing Does because you don't want to dwindle the population.
Plus most guys would be easy to lure if Scarlett Johansson said she wanted to eat them.
I think the point illustrates that even advanced Alien's can have discriminating tastes, a social hierarchy (using Alien women to do the dirty work), and an indifference to an organisms suffering.