Telomeres are intentionally shortened by the body, a process which is no doubt favored by evolution. While we don't know why for sure, it is entirely possible that telomere shortening actually lengthens life.

As telomeres become shorter, cell division becomes slower and metabolism decreases. This means that an older person's cells will reproduce at a slower rate than a younger person's in general. If we suppose that every cell division poses an equal chance at producing a life threatening cancer, then slower cell reproduction at a higher age would likely be beneficial.

Of course this is just speculation, but likely there is _some_ health benefit to telomere shortening otherwise we would not have evolved to do it.