Someone earlier said it perfectly: why do most people use gimbled pulses/bursts and multi-cannons?
Because the Game Designer has made every other weapon so power-hungry (beams, rails), so susceptible to heat overload (rails), or so easily countered (dumbfires, torpedos) that it's little wonder that there's hardly any variation between loadouts.
(Heck, even after trying them I couldn't determine the reason Bursts even exist.)
We get 12 different doodads for internals that add buffs for hulls and shields - but most of the population probably uses the same 3-4 weapons.
Even some of the PowerPlay weapons... "God no, we can't have Extra-strong Weapons that EVERYONE can't buy in EVERY station! Make them purple, and fire faster, but do the same damage as anything else... oh, and don't forget to make it take a million megajoules to deploy."