I don't think this is true for many types of insurance. In many cases, insurance companies can "go after" a perpetrator, like in car accidents and credit card fraud situations, but what about home insurance that covers fire/flood/acts of God? What about life insurance or health insurance?

In these cases I am pretty sure the insurers make their living by shrewd actuarial rate-setting that tries to make their "average" policy profitable, and by having a large enough customer base that the "average" case is statistically likely.

The way to make BTC insurance work would be similar: calculate the costs to replace BTC, times the likelihood of needing to, and charge more than that.