You could also make this point with illegal immigrants.
With ICE simply looking for "Anyone they can excuse grabbing", all violent/gang-affiliated immigrants have to do is exercise basic caution, and ICE will miss them completely. If they have enemies, or witnesses in immigrant communities that could testify against them, all they have to do is leave ICE a tip against that person.
Ok i dont know the stats, but serial killers are not as common as drug cartel and human trafficking right? Not sure which is worse or anything... but serial killing is usually only profitable to the entertainment industry.
Like all horrible, but we dont ALSO have a lot of serial killers do we?