Given the egotistical nature of the Goauld I wouldn’t put it past them to have a sort of “gentleman’s agreement” to keep war mostly ground based to help limit the ability of the jaffa to rebel. We never see any Goauld weaponry that can track its target for instance. Everything just shoots in a straight line until it hits something. They want “war” to be up close and messy to help control their subjects. Given that, air defense as we understand it would defeat the purpose of fighting in the first place for them.
Shooting two guns at the same time does in fact look cool. That’s not a myth. Hitting two targets with two guns at the same time is really hard though.