> CAT bonds are generally tied to the specific natural hazard ("this bond triggers if a hurricane of Category 3 or higher land falls in this segment of Florida") or to industry losses, as estimated by an agreed upon source.

A big part of the reason for this is that if payout is tied to actual loss, it starts to look a lot like actual insurance, which is specifically not what you want. Because while anyone* can buy a bond, only insurers or reinsurers can write insurance. This is something that needs to be considered whenever an insurer (or anyone, really) tries to transfer risk to a non-insurer.