Sidearms are generally quick-fire weapons with above average Rate of Fire. Unfortunately, they do not have high power and only have average ammo which cannot usually support the amount of ammo needed for high fire rate. Sidearms are used occasionally and are overlooked because of the variety of better choices. Sidearms are only used when you are reloading, or just when you just want to use it.
Side arms are another example of being shield-drainers. They are not used to destroy health, but weapons such as the burst torch can drain shield easily, allowing other weapons to make a quick kill. It is better to use these weapons to drains shields as they are not as useful as other weapons, so it is best to use them instead of wasting the ammo of other weapons.
They are also mainly used to finish off an enemy that is low on health, so as to not waste the ammo of better weapons.