This is not strictly true. You have lots of evolved repair mechanisms to fix the damage caused by sunlight. It's only when they get overwhelmed that you accrue

This is not strictly true. You have lots of evolved repair mechanisms to fix the damage caused by sunlight. It's only when they get overwhelmed that you accrue permanent damage. It's still a probability game, though. Note that if we didn't have UV repair mechanisms, we'd blister in a few minutes.