Why do keepers not wear a hat in sunny climates?

Said it before and will continue saying it Why do keepers not wear a hat in sunny climates? Just been to a huge event here in Southern California, San Diego Surf cup Not one hat ‘ OK for referees, coaches and parents to protect themselves from the sun but keepers no. I have seen many keepers stand with their hand over their eyes giving some shade but why not wear a hat,  even though the rules state a hat may be worn but needs to have a soft rim.  Maybe some sort of fashion statement as hats may not be cool because Baseball players wear them.

I wore them most games while I played professionally in the sun, rain and even better in night games to stop the glare from the floodlight. I reckon if one US national team player wears it the rest would follow like sheep.