There are numerous reasons for the decision I'm sure, however the most obvious answer would have to be that the earliest settlers were attracted to the Great Plains by the abundance of game as well...
The Great Plains lacked everything that Americans considered necessary for survival---access to water, wood in the form of forests, good soil to grow crops, predictable weather, friendly inhabitants,...
I don't know. I'm pretty sure it's "There was one for spring and another summer." but I'm pretty sure they weren't made from buckskin. :) DON'T JUDGE ME BECAUSE I PROBABLY GOT THIS ANSWER WRONG. :)...