Wow double entendre or what?
I can think of several reasons why good head is important…but probably none of them relate to beer.
Seriously though, at the golf club I used to wait at back in the day, the bartender told me once what the importance of a head on the beer was…but I was too busy ogling one of the female servers.
Head-related story (from the same golf club)
One day, my service captain (basically head waiter, but fancier title) was ordering a beer for a club member and the bartender was on break. Our new floor supervisor was attending the bar and got the beer for him. When she (supervisor) gave the beer to him (service captain), he made a comment about the head on it to which she replied “I’m always up for a little head…”, and promptly licked her lips then flashed him a grin…to reveal the huge gap in her teeth where some were missing!