Thanks Tom for starting this topic.
You already mentioned very well, my first concern with respect to insurance: you get credits, but crafting/buying another ship still is a challenge.
I also have a second concern: only the hull can be insured, but a hull breach makes one loose all equipment attached to the ship and all equipment in the ship store. This equipment is potentially a much bigger value than the hull, especially for tier 1 ships.
I will give a small example on my last hull breach, I lost this equipment with estimate value between brackets:
Hull: Polestar - 783K
Mining: 2 Needle Core Laser - Kali (2 * 333K)
Shield: 1 Krala Field Shield KFS3 (415K)
1 Defiant Shield DS-1 (mission item! - not repraceable)
Reactors: 1 Tokamak CE Series 2 (650K)
1 Bussard Generator Series 3 (3250K)
Systems: Kryton Mining Scanner Class 5 (100K)
Prams Armour Repair PR1 (mission item! - Similar item Vortan Armour Repair S1= 300K)
So, the hull breach costed me an equivalent of 6.2M credits of which an insurance will refund me a max of 783K for the hull or only 12.5% of the total loss. For the other tier 1 ships (deepcore/frontier/raven), the percentage would even be lower.
(and if I take into account the 1/3th cost of the insurance itself, the percentage will even be lower)
Conclusion: The credits for the tier 1 hull is the least of my problem when facing a hull breach. The main issue is gathering all the required resources for crafting new hull AND more importantly all the mounted equipment.
It's a bit like with an home insurance. In case of a disaster, not only the construction has to be rebuild, but also you have to repaint and refurnish the house. But the things you care about most, like the family pictures are lost forever.