Also I think they pop up so often because they have became one the three defining features of what makes mobile suits different from everything else. There are the remote weapons which have become so tied with Gundam that they don't even try to explain them anymore they are just there. Next is the beam saber which is the beam saber. The final one is something that may just be me, but the thruster laden backpack. I have come to notice more often than not a mobile suit will have it's main thrusters in a separate unit on it's back. I think this is why the S1 designs were so engaging, there were no backpacks. I have to think it was on purpose considering how ridiculous backpacks got in SEED.