It still applies because while organisms all have some form of self-repair ability, most do not have complete self-repair. "Wear and tear" is still possible at

It still applies because while organisms all have some form of self-repair ability, most do not have complete self-repair. "Wear and tear" is still possible at the macro level where self-repair is missing or slower than the damage rate -- famously in the articular cartilage, for instance. There's also accumulating damage that does not resemble mechanical wear and tear: toxins, misfolded proteins, DNA damage/mutation, senescent cells, etc.