there is nothing a 7mm rem mag can kill that a 30/06 can't. Unless you are shooting over 400 yards there is no need for the 7
Just how far do you want to take that argument?
There is nothing the 30-06 can kill that the 308 can't.
There is nothing the 308 can kill that the 300 savage can't.
There is nothing the 300 savage can kill that the 30-30 can't
Those are great arguments for KEEPING a gun you already have...not for eliminating choices when shopping.
You are right that the 30-06 can do a lot. But then, the list of cartridges that can do a lot are as long as my arm.
The 30-06 and the 270 winchester are very similar, yet I often hear guys saying the 30-06 is a bit more powerful. It is. Thing is, there is a bigger gap in power between the 7mm remington magnum and the 30-06 than there is between the 270 and the 30-06
The 7mm remington magnum shoots a tad harder and shoots a tad flatter. For something like elk, this extends your range a little bit, and it also makes range estimatiom a little more forgiving.
The average deer hunter absolutely does not need a 7mm remington magnum...but then he doesn't need a 30-06 either.