"Because the work makes the weapon more expensive. Corporations and government agencies are concerned about the bottom line first. Look at all the aftermarket parts and accessories for cars or trucks. The manufacturer turns out a basic product and the consumer customizes it for their needs."
If I were an attorney needing to refute this, I think I would ask why you need this but police agencies all over the nation use this gun without these mods. If it's good enough and safe enough for them how come you need to be different? And, if these are such good mods, how come the factory doesn't make them that way to start with?