Most navies have mothballed fleets that are only activated in time of war or expectation of same.

Being The Imperium is in a constant state of war would it stand to reason that they simply have no ships to spare in the first place?

When we talk about the fleet in Sol it's always mentioned that it is an absurd amount which accounts for a high percentage of the most modern ships they have patrolling this single system which also has plenty of immobile defensive perimeters.

But if you went to Mars, would there just be hulls floating around or lazily tethered to some out of the way spot to make room for new ships being built or existing ships needing repairs?

I'd love to know anything about these forgotten ships.

I'm also curious if the majority of cutting-edge ships were in fact made per-herasy or something and they're just built so much better than anything The Imperium can slap together in 40k?