Ernest T,

I think part of the reason is that calibers like .223 and .22-250 and even 6.5mm CM and .308 can shoot bullets over a fairly wide weight range.
My .223s have shot bullets from 35 grains to 77 grains for example and even my 6.5mm CMs have shot bullets from 123 grains to 147 grains.
Just for grins, measure the bullet lengths of a .35 or 40 grain .223 and a 77 grain .223. The light bullets would fall out of the neck if you tried to seat them for a short jump.
In my rifles, the 77 grain bullets can be seated into the lands but if I tried that with a 52 grain bullet it falls out of the neck.
By the way, my rifles shoot the light bullets very accurately, even if the jump is incredibly long.
But if the chamber was short enough to seat a 52 grain bullet near the lands, the 77 grain bullets would have to be seated back so far into the case that the pressure would be much higher.

The weight range of 6.5mm CM bullets is not as severe, but there is still quite a difference between the length of a 123 ELD-M and a 147 ELD-M.
I suspect that the manufacturers are trying to accommodate all of us, those who shoot light bullets and those who shoot heavy bullets.