Which always seems a bit odd to me - didn't the yorktown or whatever have a proud history? a captain that was proud of it? etc etc.
Starfleet wanted to make a gesture to Kirk by giving him an Enterprise, so they had to rename the Yorktown. I would guess that the Yorktown name would soon pass to a newly constructed ship, perhaps an Excelsior.
This is my theory, I believe an Excelsior was already set to be christened Yorktown, either one already in final trials or soon to be constructed. A simple trade off in legacies.
The name Enterprise is given to the old Yorktown and the legacy of the Yorktown is the passed to the upcoming new ship to carry the name.
It makes sense that theory would give Starfleet and the Council a little wiggle room to trade names like that. To satisfy those who support the honor and history of the Yorktown and to reward Kirk and his crew...
Just my two cents.
Vons
Works for me.