Trust me, I'm weird in my own right.....I've learned to live with it..... 🤣 The 06 has more velocity, thus shoots flatter with better ballistics. And the ammo is more available
More velocity/flatter shooter/better ballistics isn't usually necessary.
If .25-06 has all those over the .257 Roberts, and is therefore "preferable", then one can say, "Why settle for the .25-06 when the .257 Weatherby Magnum or .25WSM shoots the same bullets, with much better velocity, is flatter shooting, and therefore has better ballistics."
I do most of my whitetail hunting with a .308, despite the fact that there are numerous .30 caliber cartridges with better velocity, that are flatter shooting, have better ballistics, and are readily available.
Then why shoot the .308? Because the .308 is "enough" for the chosen task. I don't need to jump up to .300WinMag, when .308 will do the job more than well.
I still hunt occasionally with a .30-30, and you don't get a lot slower in an available .30 caliber than that. I wouldn't even try to guesstimate the number of game that has been taken in America with the thutty-thutty.
I don't need the extra 200fps that .25-06 has over the .257 Roberts, when it will be used to shoot whitetail out to several hundred yards. All the .25-06 is gonna add to that scenario is recoil and noise.
There are definitely tasks where the .25-06 would be the better tool. If you don't want to handload, then .25-06 would definitely be a better choice.........but if I were basing MY criteria on availability of factory ammo, I wouldn't consider .25-06 at all.
I'll admit, I like to be different at times. When I looked at calibers for my dedicate elk bolt action rifle, I went with .280 Remington Ackley Improved, instead of 7mmRemMag, despite the 7Mag shooting the same bullets 100fps or so faster than the .280AI. I've taken 2 elk at 400yds with it so far, and I wouldn't have bagged them any cleaner with the "better" caliber.