During Freespace 1, the ML-16 was selected as the primary armament of GTA strikecraft due to a need to simplify logistics and provide an easy to use weapon that pilots with limited training could use effectively. The "ML" designation stands for "medium laser" and was used as a classification in conjunction with the "HL" or "heavy laser" and the "SL" or "small laser" designations. This meant that the GTA likely had more powerful laser weaponry that could have been pressed into service, some of which were notably more effective against Shivan shields than the ML-16. Rather than restarting production of HL weapons, the GTA decided that it didn't want to interrupt its planned logistics and to wait until the introduction of the Avenger cannon. Once it became clear that the Shivan was an existential threat, this policy of logistics simplification was thrown out the window, resulting in the huge development of ships and weapons during the first Shivan Incursion. Many of the ships and weapons developed during the First Shivan Incursion had been in development for years, with their deployment and production being deemed unnecessary during the Terran-Vasudan War.
Special Terran Intelligence units may have been issued limited run HL weaponry. These weapons were expensive to manufacture and consumed large amounts of the strikecraft's power supply, requiring skilled pilots to use effectively. Nonetheless, they were invaluable for special ops missions during the early stages of the Shivan Incursion. The decision was made to hide the deployment of HL weapons as every frontline combat unit would begin demanding the procurement of HL weapons for their squadrons and the resulting controversy over the decision to wait for the Avenger cannon would result in massive morale issues during a critical point in the war. Subsequently, any kills by Terran Intelligence pilots using HL weapons were off the books.
By the Freespace 2 era, the GTVA once again attempted to standardize its logistics train due to peace time budget constraints. The HL-7 was adopted as the primary armament for strikecraft, although provisions were put in place to quickly restart production of heavier/experimental weapons should the need arise. The Prometheus R, despite its lackluster performance, was kept primarily in production because the factories could quickly switch to the production of the original Prometheus S if sufficient resource deposits were found or if the need outstrip the high costs of its production.