i see this happening very easily:

i lost all my bitcoins, i had 1million of them. the thief moved them from 1yyyyyyyyyyyyyyyy to this address 1xxxxxxxxxxxxxxxxxxxxxxx
and now my 1yyyyyyyyyyyyyy is empty. lets make a claim



.. now to use the private key i have secretly stashed away for the 1xxxxxxxxxxxxxxxxxxxxx that i pretended not to own.

<3 claims later from random people>

insurance company have no more new insurance premiums's coming because the openly viewable insurance wallet is now empty. they can no longer guarantee payouts and everyone asks for a refund of their premium.

insurance company is now bankrupt

now tell me how will an insurance company prove or disprove a theft and that thief is not also the claimant