There is no reason not to own a 30'06 that I can think of.
Sure, there are cartridges out there which can "almost" do what the '06 can but why compromise.
That's like saying, "a Fiat does 90% of what a Ferrari does, so I own three old Fiats and two rusty Alfas instead of a Ferrari"

Besides, the selection of bullets for the '06 is huge so it can fill a very wide gap between your 7X57 and the .375.