Let's say hypothetically that you have a number of large trees in your back yard and that it would cost several thousand dollars to remove them. Let's also say that very large branches occasionally fall from these trees with force enough to kill people. Now, as an insurer for the property, would you rather wait out the people-crushing and receive big claims for property and life damage, or would you pay the much smaller cost of having the trees removed?
Now imagine you are a health insurer. Let's say that early detection and removal of cancerous skin growths costs one tenth of the average insurance claim for one detected late. Let's also say that a yearly skin checkup costs a negligible amount per person. Would you allow small claims for regular skin checkups, or would you wait for the larger, but less frequent, actual cancer claims?
Unfortunately I think it would often be worth more money to the insurer to wait for the larger claims.
Mokalus of Borg
PS - You'd need actual statistics to prove it, though.
PPS - And the it's their job to know that kind of thing.