>>212151951 (OP)most of those big capital ships and basestars have defensive batteries like "flak" or some kind of point defence, but there are times when those systems go down, or might be destroyed, which would allow the enemy force to easily bypass the defences and destroy the big capital ship with ease.
vipers were used as a screening force, they destroy the shit that can destroy the point defences, and cover areas of the ship that lose the point defences for whatever reason.
conversely, you would use vipers to attack an enemy capital ship outside of the range of that ships point defences, then use the bigger guns on your capital ship to blow up their point defences, then use your vipers to exploit the gap in their defences.
what this all boils down to is having huge dogfights in the middle of the battle while the capital ships slug away at each other, so that both sides can react to gaps in defences, either defending or attacking.
thats BSG tho. star wars is literally retarded rule of cool shit that makes no sense. i guess you could argue that the rebel alliance doesn't have big enough capital ships to do much damage, so using fighters as a screening force is pointless.
in babylon 5 the fighters are used as a "shield" to cover vulnerable areas of ships and the station itself, which is a more pragmatic approach, but sort of depressing if you're the pilot.