Self-interest. In order to preserve the continued success of the Alcor company.
In order for people to continue buying cryogenic services, the company would have to be able to demonstrate that it's actually doing what it claims to do (keep the bodies frozen and stable). As soon as that stops, nobody would ever trust them with any business, ever. And as soon as revival is possible, it becomes the cheapest option, versus incurring the ongoing costs of preservation.
In order for people to continue buying cryogenic services, the company would have to be able to demonstrate that it's actually doing what it claims to do (keep the bodies frozen and stable). As soon as that stops, nobody would ever trust them with any business, ever. And as soon as revival is possible, it becomes the cheapest option, versus incurring the ongoing costs of preservation.