I understand why he wouldn't want to do that from an artistic stand point since authors would never consider selling only certain chapters of their books, but I think he's making a mistake. The only people who will buy the full album are true country fans and if any of his songs hit the radio, average people won't be able to buy them cause they won't want the whole album. He will lose a lot of money.
The year is 2014, not 1980 - people simply won't buy an entire album now. It's easy to decide you like a song, and buy that individual track by one of the many methods available. It's also cheap enough for most people to take a risk if they're unsure. But a whole album? People won't buy it, and it's arrogance to assume they will.
Garth Brooks' refusal to sell tracks individually is a bad business model in the digital age. People, generally speaking, want to have the option to "try it before you buy it." Requiring people to purchase an entire album without being able to purchase and sample a few tracks will prove to be detrimental to Garth Brooks' sales.
The digital model of selling individual tracks has become the new norm. While Brooks may generate more profit from strong fans with his strategy, he deters more casual fans from buying songs. In fact, obstinance about making digital songs available for purchase could lead to negative stigma in the music marketplace.