To an extent, I've been wondering the same thing. I suppose it's so that people don't make characters that are "too exceptional", but I think even that is kind of an odd thing to want in a game where players are big-damn heroes fighting big-damn horrors. It's especially confusing when you remember that a number of the mods in there, even if not bought at creation, can be purchased later for a morph you want, or even gotten as an implant. There isn't too much that you should worry about with traits, but do note that someone who takes them all will have a ton of minor bonuses (sometimes major, up to +20) to virtually everything. Inform your players to keep track, because that's going to get very annoying very quick for you.