Conventional weapons may seem useless in a world where firearms - and sometimes even mechanical walking engines of destruction - are used on a rather regular basis.
There are a good number of reasons as to why these weapons still exist and are even still manufactured.
- Technology is not always a viable weapon. Against a wizard or psionicist, a gun crafted by a lower-level technologist will be largely ineffective most of the time. Any amount of TR will prove difficult for a firearm to penetrate, unless it was constructed by a relatively (to the level of the being with TR) high-level technologist who chose to increase its base student level. A sword, however, suffers no such difficulties.
- Technology is not always seen as honorable. There are a multitude of cultures in the world that train and maintain high numbers of knights or samurai, two classes which will often see the use of firearms as dishonorable due to the lack of skill required (though a gunslinger would argue that point).
- Unless the wielder is a gunslinger, guns are largely ineffective in close quarters. Mechanically speaking, firearms draw attacks of opportunity, do not allow the wielder to make attacks of opportunity, and require reloading. While a gunslinger is able to avoid the first two difficulties and is often wielding a weapon which makes the third an almost non-existent problem in a single combat, most adventurers who use guns will also carry a more regularly-seen melee weapon once the enemy is engaged. Even gunslingers will sometimes use melee weapons, as ranged weapons are not always effective, and there is always the chance to run into someone with technology resistance (see reason one, above).
The role of the front-line fighter is not non-existent in Trinity, nor is it required that every character in a party use firearms. While they are usually more effective than other weapons in terms of raw damage capacity, most people in the world are not proficient in their use, while others outright distain them. In the end, however, it is a matter of practicality: with two of the more common Force-users in the world being resistant - to some extent - to firearms, it only makes sense for more conventional fantasy weaponry to exist.