What's more imposing to freeport invaders - some eagles, or a Juggernaut which in RP is mysterious and extremely intimidating?
Have you seen it used as a war vessel? Against who, I might add? Against Nomads and Wilde? Sure, that's a proper use of it, to defend Zoner installations against enemies.
Edit: Many things in game require suspension of disbelief. Planets and stations being so small, battleships being so small, the physics, the weaponry, the ships flying the way they do, the way ships are designed in terms of space travel, etc. The Juggernaut's mysterious reputation is another thing for you to imagine, not base off in game activity which does not accurately depict the true Discovery universe.