Care to cite an episode where a Federation vessel takes out the surface of a planet? :P
Just as Federation ships carry enough firepower to scorch the surface of a planet (stated in dialogue), a shuttle hitting a planet at many times the speed of light is going to mess up a planet if it hit. Simple physics there.
Just the fact that we're dealing with ships that move faster than light speed will necessitate standard weaponry (even defensive) much higher than what we today deem as military only.
A starship is built with the firepower to obliterate a planet. A shuttle isn't, it may be possible to do some damage but that's not its intended purpose. In "A Taste of Armageddon", they aren't going to ram the Enterprise
into the planet at warp. They're going to use phasers and photon torpedoes to achieve their goal...
A Taste of Armageddon wrote:
SCOTT: All cities and installations on Eminiar Seven have been located, identified, and fed into our fire-control system. In one hour and forty five minutes, the entire inhabited surface of your planet will be destroyed.
-class starship is sent when Outposts along the Neutral Zone go quiet. A Constitution
-class starship is sent to engage Klingons in the opening salvo of a war. We watch them go toe-to-toe with starships from other Empires, that's their job in a time of war.
Technically, they aren't 'warships' their 'multi-purpose explorers'. Which is why describing the Vengeance
as Starfleet's first 'warship' isn't a problem. But it doesn't mean Starfleet had been pacifists up to that point or were pacifists in the Prime timeline.
Journey to Babel wrote:
KIRK: Starfleet force is used only as a last resort. We're an instrument of civilization.
And with they can bring an awful lot of force with a single ship.