We're a leadership conscious army and they can always take the other basic weapon options instead, just not those other options and the sgt kit. It's also cheaper than any other armies sgt upgrade, and they are valid targets for the other character effects for first prince powers. I think it's worth 15pts to make one of your dark lances master crafted on a balestrike band, or 35pts to bring a multiphase key generator in your deepstriking falcon. CWE have exarchs and warlocks as Sgts. Harlies have troupemasters. Corsairs are like DE sgts in that they're highly situational.