Setting aside airline hats for a minute I started wearing hats about 25 years ago. They keep the weather off (rain, sun and everything between), keep your head warm when it's cold, the brim can be adjusted to keep sun out of your eyes (much more effective than a visor when driving a car). I am a particular fan of Tilley hats (Canadian but available in the UK).
And, on the subject of sun and going back to airlines I watched a captain, as he started his approach, take off his headset, put on his sunglasses, a baseball cap and then put the headset over the ensemble. Finals was direct nto sun and he pulled the peak down to help keep the sun out of his eyes. Yes, it wasn't his uniform hat (I don't know if he even had one) but ........ Maybe some of you need a company baseball cap with a nice long peak!