I can almost guarantee you that your ordinary feature developer working on a deadline is not thinking about that. They're thinking about how they can ship on time with the features that the salesguy has promised the client. Inverting that - and thinking about what "features" you're shipping that you haven't promised the client - costs a lot of money that isn't necessary for making the sale.
So when the reinsurance company mandates a checklist, they get a checklist, with all the boxes dutifully checked off. Any suitably diligent attacker will still be able to get in, but now there's a very strong incentive to not report data breaches and have your insurance premiums go up or government regulation come down. The ecosystem settles into an equilibrium of parasites (hackers, who have silently pwned a wide variety of computer systems and can use that to setup systems for their advantage) and blowhards (executives who claim their software has security guarantees that it doesn't really).