I suppose because they are so easy to use for so many things. No drama unless you start talking about what is the best load for something.
I came to the .30-06 by using a .300 Savage for about eight years and then a .308 Win for about the same length of time. I am glad I did. Easy to load for, easy to use.
Of the big game types I have killed, I have used an '06 on at least one of them with the exception of a bear. I need to take care of that.
Match the loads to the quarry and life is good. I have lots of other centerfire chamberings but except for the .223 and rarely the .338 Win Mag none get much use in the field.
Just say it. Its not a 308 Norma mag.. Plain and simple. That's why its boring..