Why do only capital ships have screens?

[Brandon C]

While I have the core rules for the GDW and Mongoose versions, as well as both Ships of the French Arm, I have noticed that only battleships on heavy cruisers mount screens despite the fact that the rules do not indicate that they can't be used on smaller ships. In particular just about any warship larger than a fighter has room for minimal screens.

One ruleset I am lacking is Star Cruiser, so I don't know if there is a prohibition there for screens on a ship below a certain size or power plant below a certain output or if this simply became "the way things are done" back then and no one was vocal enough asking "why?"