Essentially it is me trying to limit how much player characters can jack up equipment.
I really don't want characters modifying their quad lasers to do twice the amount of damage they normally would.
I also want to add a bit of a twist by making modified gadgets quirky.
I am also trying to make the engineers job, which we have a player in the game specifically devoted to engineering, interesting.
So it is three things. I am trying to limit the uber stuff that charactes can develop for themselves, add some realism, and add a general sense that messing with things gets you potential problems.