We aren't all human, there are Andorans, Quinlions, any race you can think of, there will be at least one Samurai in some solar system out there.
We don't have a unified code of ethics, some of us have strict moral stances, but many more have no qualms about doing anything immoral, illegal, whatever.
We don't use swords, laser or otherwise, at least not exclusively. We don't pledge ourselves exclusively to one noble, we don't kill ourselves over failure, we don't even dress like them.
We just kill people for money. And it's a cooler name than assassin or thug.