The sun ages your skin. It makes you look older. I've known people in their 40's who have avoided sun who look like they're in their late 20's. Their skin is supple, has few wrinkles, and generally looks healthy. My friend is my age, his wife is 10 years older than he. She legitimately looks a good 10 years younger than him thanks to intentionally avoiding the sun throughout her life.
I, in contrast, look my age (40's as well), because I've spent a reasonable amount of my life outside. Chores, being raised with an attitude of "don't come back inside until dinnertime", and swimming competitively in the summer. My skin doesn't heal as well, it's less supple (sub-skin features show through more harshly than they used to), and I have a fair share of wrinkles around my eyes and corners of my mouth (charitably referred to as laugh lines).
And then there's the extreme sunbathers and outdoor laborers who look like they're in their 70's at 40; who have already had potential cancerous spots on their skin removed.
It's simply one of those things where even moderate exposure can do demonstrable damage to your skin. And if not treated quickly, the cancer sun exposure causes can straight up kill you.
Finding out that it may also have positive benefits feels weird. It feels like learning that regular exposure to acid has long term health benefits.