Pretty much every baseball-style cap comes with a button on top. Does it have a purpose? Is it simply fashion? Would buyers reject buttonless caps?
I believe the button is there to hide the spot where the seams join. Without the button there would be a jumble of threads which wouldn’t be very attractive.
Makes sense. But I have a couple of caps handy from which I’ve removed the button. One has a rather tidy convergence of the 6 gores that make up the “dome”. The other has a well-executed miniature buttonhole.
A baseball coach I once had in high school declared that if the button is the same color as the crown of the hat, it’s a “cheap hat” whereas if the button is a different color it’s a “nice hat”. But then again, he also said that if the sweat stain reaches the end of the bill you’re “sweating for the cycle”.
I wore a fitted baseball cap with a button to a pet store one day and stood with my back to a large parrot. He reached down with his beak (bill?) and plucked the button clean off my hat.
I actually like it better that way. No jumble of threads, the panels meet very neatly in the center.
As a tall glider pilot, I can assure you that the purpose of the button is to put a divot in the top of your head when turbulance causes you to hit the canopy, and remind you that you should either remove that %&#ing thing, or use a different style cap when flying.
It’s there for protection against critical hits.
When my friend shot me in the head with a bb gun whilst I was bending over to make a snowball, the little button took the bullet for me as it were. It had a little dent dead center where the bb hit. My friend claimed he was aiming for it, while I maintained he was lucky that it didn’t injur me and force me to kick his ass.
[Removing baseball cap, grasping it by the visor, and flipping the button down smartly on the OP’s exposed head]
That’s what the button is for!
So - have any of you wiseguys ever uncovered a button to see exactly what was in there?
See posts #3 and #5
Or do you mean under the cloth covering the button itself?
This is exactly why I remove them - unacceptable when flying a glider.
When I was a teenager, I had a pickup truck that was badly in need of new shocks. I’ve experienced that divot in the top of my head as the roads here are bad and I often hit turbulence and hit my head on the top of the canopy. 
I just want you to know I’ve been giggling at this for days.
When I was in high school, the baseball coach told us that the button is there to show if a fielder is fielding a ball properly. He taught us to charge the ball and stay in front of it, with the proper fielding position to be your chest at around a 45 degree angle to the ground, and your eyes looking down at the ball as it goes into your glove. The reason for fielding the ball this way, instead of off to your side, is to help keep the ball in front of you if it takes a bad hop.
If you do that, the top of the hat, and thus, the button, are visible.
Whether or not that’s the real reason (I personally don’t think so), I don’t know. But I do think it’s a good training tool for infield 101.
cf’75
Tough neighborhood.
As I wear ballcaps pretty much constantly, and I’ve never had a bird land on my head, I just assumed that the button was there to scare off the birds.
If that’s so, it doesn’t work (see my previous post).
The parrot didn’t land on your hat, did he? 
Well, he went for the button instead of you, didn’t he?
I see… so the button is a decoy, to keep the bird from landing on your head and, presumably, pecking out your eyeballs. In that case then, it worked beautifully.