Because cowboys eat with their hats on.
Also:
A cowboy rides into town, his face chapped and raw from the wind. He dismounts at the saloon, walks his horse up, and to the astonishment of the men on the porch he jams his finger in the horse's ass, swirls it around, and wipes it on his lips. A man on the porch asks, "Is that some kinda cure for chapped lips?" The cowboy answers, "No, but it sure keeps me from lickin' 'em."
And then:
A young gunslinger is in the saloon getting shooting advice from the sheriff. The sheriff says, "Cut a notch in yer holster, son." and the kid asks "Will that make me draw faster?" to which the man nods. The kid pulls out a knife and cuts the notch, and sure enough when he draws and shoots the drink off the piano it's faster than ever. The piano man stops and the bar quiets, but when they realize it's over everything goes back to normal.
The youngster begs for more hot gunslinging tips. So the sheriff says, "Hang her gun belt just this way." and the kid asks excitedly, "Will that make me draw faster?" and the old man nods. The kid adjusts his belt, stands ready, and draws and shoots the tip jar off the piano.
The kid is real excited at this point. He asks if the sheriff can give him any more advice. The sheriff says, "Yeah, take some grease and cover the whole gun with it." The kid asks dubiously whether that'll help him draw faster. The sheriff replies, "No, but it'll sure make it easier on you when Wyatt Earp over at the piano shoves it up yer ass!"
An old cowboy walks into a bar and orders a drink. As he's drinking, a woman sits down beside him. She asks the cowboy, "Are you a real cowboy?" He answers, "Well, I've spent my whole life on the ranch, mending fences, herding horses and branding cattle, so I guess I am." She says, "I'm a lesbian. I spend all day thinking about women. When I get up in the morning, I think about women. When I'm at work, I think about women. When I'm in the shower, I think about women."
Later, a tourist walks into the bar and, spotting the cowboy, rushes to him excitedly. "Are you a real cowboy?" he asks.
"Well, I thought I was a real cowboy," says the cowboy, "but it turns out I'm a lesbian."