After 25yo the sun bathing can really take a toll on your skin

[Noodlewhore]

When you are a teenager your skin is good, won't be affected much....lots of collagen, cell turnover, subcutaneous fats, elastin ecc
After 25yo if you don't put enough sunscreen your skin will start to appear sagged, with wrinkles, and you will age like shit.
SPF 50 is mandatory after 25yo and highly advisable under 25yo

 

[Effortless]

SPF is mandatory at any age.