I was watching an interesting video on "eye color". Apparently, early on blue eyes emerged in northern Europe as a mutation that helped people see better at dawn and dusk, and so gave them advantages when hunting at dawn and dusk.

But at the risk of sun damage since the brown pigment most people have protects the eyes from sun damage. But apparently the trade-off was worth it genetically speaking and blue eyes flourished.

But then "farming" displaced hunting and the genetic benefit of blue eyes largely ended. But by then "blue eyes" had become preferred and so, long after the functional advantages of blue eyes were gone, the advantage blue eyes in attracting mates continued to cause blue eyes to become increasing prominent among some Northern Europeans peoples.

Whether this theory is true or not, it is an example, of a physical attribute may contribute to attractiveness which does not seem to have much purpose today but may have had purpose in the past.