I think it's a great idea and would love to see that happen. They can make drivers carry insurance, so it's not outside of the realm of possibility to make cruisers do the same. It's unlikely to happen now, but not impossible in the future. Who knows, we might just be a pandemic away from such a requirement. It would help improve public safety because it would at least reduce people's likelihood to lie on those forms, thereby spreading communicable diseases.
There are plenty of reputable insurance companies, btw. My
travel insurance company of choice is great. Affordable plans, and on the two recent occasions when I had to cancel trips (one for medical reasons & one "cancel for any reason" cancellation), I submitted the required documentation and then was reimbursed promptly.