They are ruminants, able to take vegetation which people can not eat and efficiently turn it into good, nutritious food. They are social animals with strong herding instincts, traits that make them easy to manage in a farm situation. They are polygamous, meaning that we need only one excellent bull to breed many cows. They fit well in our climate. The most important difference between cattle and elk is summed up in the word seasonality.
Elk are still much closer to nature.
They have strong seasonal cycles in breeding activity, feed requirements and general management requirements. Elk bulls are only capable of breeding from about August to January, and the cows cycle only during that same period. In order to grow antlers, elk bulls must have very low levels of testosterone in their systems. In January, their testicles begin to shrink, and their entire reproductive systems slow down. During the rut, the breeding season, they can be monsters.