According to the study cited, they concede that annual checkups result in more diagnosis, but not in a decrease in morbidity. What you consider worthwhile, or worthless, is up to you I guess.
More relevant for the insurer (which might help explain why an insurer is urging checkups) living until 80 with diabetes and on dialysis is much more expensive than living healthily until 80.
The point is that knowing you have a disease allows you to treat the disease, which one would hope would reduce your chances of dying or becoming disabled.
The point of the comment you're replying to is to explain that didn't happen.