Why is the lifetime of a skin cell so short?

Its a matter of turnover. Your skin does many things but its main action is a "simple" mechanical barrier to the outside world. So unlike, for example, a liver cell which is producing many proteins and enzymes, a skin cell on the outer epidermal layer just has to sit tight and act tough against whatever comes in contact with it. Throughout the day that will be your clothes, soap, bacteria etc. Inevitably therefore your cells would get damaged incredibly frequently. So the surface of your skin actually consists of dead cells which can be easily rubbed off throughout the day thus preventing damage to the more sensitive bits underneath. So why is the lifetime of a skin cell so short?, because that way we dont end up with constant sores and damage all around our body.