Oh, another thing I forgot to mention was that later on in the series you have Minovsky-particle-lattice based deflector shields, which are quite effective at blunting the usefulness of the direct-fire particle-beam weapons that had become the standard for ship-to-ship combat by then. Hence, it becomes more important for a mobile suit be able to get in close and use armor-piercing melee weapons from inside the shields. They're only really stuck on Super Prototype Bullcrap in Mobile Suit Gundam, but they become reasonably semicommon in sequels, to the point where it's often a tactical choice to employ a beam weapon or a more old-fashioned but potentially more useful high explosive shell, even though you can't really guide either remotely.