True that, but a fleet should still have several different ship classes all the way from huge heavy-hitting battleships to small scout ships. Sending a Star Destroyer on duty that could be handled by a much smaller ship is wasteful, something an Empire should also be mindful of.
Which is why they send a Terminus
-class frigate instead (the smaller capital ship). As for scout ships, there's the Fury
-class interceptor (SI and SW starships), but they don't tend to sit in orbit a lot - they'll either be docked aboard a capital ship or out actually doing stuff.
Not to mention specialized ships for different needs that can handle their area of expertise much better than a standard design meant to do a bit of everything.
True enough - but then, a specialist vessel would generally not be with the main battle fleet. It'd be off doing whatever it's specialised to do, or prepping for a mission. Unlike regular warships, the "fleet in being
" concept doesn't much apply to specialist vessels, even if they're well-armed.