Well, there are many reasons. The most obvious is safety. Wilderness travel is inherently dangerous. Beside the possibility of accident or bad weather, knowledge of water sources is very important in the arid Southwest. Even high elevation areas can be life-threatening when drought adds to the difficulty of scarce water supplies.
Experience is critical for a guide.
Eb went on his first solo winter camping trip as a Boy Scout at the age of 14. He has fought forest fires in nearly every western state. He has done timber inventory work in the forests of Arizona and New Mexico. He has hiked uncounted weeks with and without companions through the mountains and deserts of North America. He has been hiking the Grand Canyon since 1971.