If you want to get ahead, get a hat!
There were certainly regional differences in what cowboys wanted or needed. For instance, some cowboys would have hats made to order to fit the terrain.
Certain areas even had their own styles, like the Montana peak hat. It's like a Smokey the Bear hat — creased in on four sides. Cowboys down in Texas preferred flat-top hats or a high crown. They felt it kept them cooler out in the heat.
Still other cowboys just wanted their hats big and comfortable — ten-gallon hats, for instance, were made out of felt.
Of course, the cowboys traveled a lot, so the styles all mixed together like an intermingling of cultures.