To be slightly more precise and because this is a very well established mechanism that gets overridden in quite a few circumstances : this is a "death clock" built into your DNA. One of several, but rather obvious and thus well known. A number of cell functions in your body are exempt from this death clock, most obviously the reproductive cells.

It causes your body to (very) slowly lose the ability to grow new cells. Also cells with shorter telomeres "senescence", which is sort of like aging : they become slower, and more brittle.

Amongst the advantages this has is that it protects against cells that increase their metabolism too high and against cells that rapidly divide (by having them senescence and die). The obvious disadvantage: it eventually kills you.

It seems likely, given that this mechanism is "deliberate" and definitely under the control of your DNA, that you live longer and more successfully with aging than without.