I really do think they should be mainly for point defense against incoming missiles. Small vehicles tend to have the following factors: they are usually made en masse, and everything about them are exponentially far more inefficient than larger ships with more room. The only real things that goes right for them are the small radar signatures they tend to have, the plentiful numbers of them, and the fact that you need very specialized weapons to fight them effectively like flak or some sort of area weapon that usually needs to be designed to fight a particular swarm. They are usually not something special in themselves, anything you put on them, you can always put a much bigger, far more efficient one on a larger ship. They do however, tie down the resources of your opponents facing you though. Both tactically and strategically, these machines while not being all that dangerous to most ships, punch above their weight in terms of how much materiel the enemy has to use to counter them.