Proficiency: This entry lists whether the weapon is simple, martial, or exotic. If an existing weapon proficiency allows the new weapon’s use, that weapon proficiency is listed in parentheses. Note that Exotic Weapon Proficiency (heavy weaponry) works similarly to Exotic Weapon Proficiency (firearms) in that it allows access to a wide range of similar weapons.
Some GMs may wish to replace Weapon Proficiency (firearms) with Weapon Proficiency (technological firearms) to further restrict access to these devices to player characters in their campaigns.
The technology guide says, "Some GMs may wish to replace Weapon Proficiency (firearms) with Weapon Proficiency (technological firearms) to further restrict access to these devices to player characters in their campaigns."
So, by default if you know how to aim and squeeze the trigger on a regular pistol then you know how to aim and squeeze the trigger on a laser pistol... but some GM's may rule it a separate proficiency.
That said, 'heavy weaponry' (e.g. rocket launchers) is always a new proficiency which doesn't exist for lower tech firearms.
Well, shooting a gun is ubiquitous, I agree. If you know how a trigger works, then you can pull the trigger on just about any gun. However, the difference between a regular firearm and a futuristic firearm is the sighting and maintenance. You wouldn't know how to correctly sight a laser rifle just by knowing how to sight a firearm with iron sights. Likewise, the maintenance and upkeep for misfires are also different. I think it's important to make a differentiation between firearms and technological firearms, because even if you understand Laser Rifles, that doesn't automatically mean you know antique firearms.
Consider the difference between rotary phones and smart phones. Generally speaking, old people can use rotary phones but can't use smart phones, and young people can use smart phones but not rotary phones.
You'd need a separate proficiency in both.