Let's put it this way: You're less likely to need a warm scarf to keep your neck warm. Well, if it's a full, bushy beard that hasn't been trimmed in months. It's like having an extra layer of warmth where needed.
I recall when I sailed for the Antarctic in 1976 we expeditioners were all busily growing beards to cope with the weather we expected to experience for the next twelve months. We all came home looking like wild men: uncut hair down to the shoulders, thick beards - and feeling very proud of our obvious masculinity . Most of us kept our beards for a least a couple of weeks after our homecoming just to show off.
Then off they came. Australia's summer doesn't suit the such hairiness.