The TIE Fighter is the basic starfighter for the Galactic Empire. Its two small laser cannons deal average damage towards the enemy while retaining average armor. Their boost is fairly decent, and they handle well with small turning arcs. (Equivalent- ARC Fighter, Droid Starfighter, X-Wing).
TIE Fighters, TIE Interceptors, and other TIE craft that normally do not carry ordinance can easily be modified to carry such weapons. This is done when more nimble ships are needed that can carry ordinance as seen in Star Wars films: TIE Fighter and The Stele Chronicles novel. Those stories may have influenced the game designers to have Imperial Scout Fighters and Multi-Purpose Fighters armed with ordnance.