It is ingrained into the psyche of U.S. hunters and has become one of the most popular big game cartridges in the world today. Ammunition is available across the world everywhere that big game is hunted. That alone makes it a top choice for traveling hunters. When I get on an airplane for a hunt there is usually a 30-06 and a 375 in my Tuffpak.
I believe that there are more factory ammunition choices for this cartridge than any other. Other cartridges may well be better for a given purpose but the old 30-06 still works well enough for nearly everything short of some dangerous game. Most folks probably have difficulty with recoil with more powerful cartridges. If I had only one rifle it would be a 30-06.