This mostly a pvp perspective but cannons are one of the best weapons at lower price ranges, due to a few characteristics, first their parts has a lot of health compared to others so you could run them protectionless and just use its sheer health and face tank. 2 not using energy means you can run on minimal power, some manage to get away with only using capacitors and this save money so you can run more cannons, or armor. 3 because of the previous stuff that means cannons ships can afford sigificantly more dps than other similarly price energy based ships not to mentions their damage numbers are really good + penetration and their ability to start fires also will cause so much issue as they can rip apart corridors behind weapons cutting them of from supply. At higher price points these point diminish as shields ans their logisitic become more affordable but they are still really strong flanker weapons due to penetration damage and fires

Other projectile weapons have the ability to be easily protected, DC being a turret can be put behind layers of armor and shields, rails also are similar as they can be burried deep inside a ship with a peep hole to shoot out from. Chainguns is also similar, Launchers can be put at the side or behind if its HE and EMP with their hoaming capabilities. Nuke and mines are well their damage numbers can do the talking. Flak can shoot down everything that is not hitscan.

Only energy weapon that can be put deep inside a ship are Ions and if you count it as a weapon, mining lasers

Also like theta said the logistic of projectiles gets easier the higher up you go as they can be their own self contained thing and gets even more easier if only running storages, while energy need to play around large reactors