It would be very interesting to see what sort of "original content" rights WEG retained if any, and if any such rights passed to Humanoids Inc.
And thus they were untouchable in any sort of practical terms in the game.
It wasn't until a later revision in the system that fighter-scale weapons had any ability to damage capital-scale ships.
(And yet as early as ANH, we see the X-Wings and Y-Wings damaging installations on the Death Star... )