^^^ I agree, it is a bit silly.
IRL navies honor previous ships Yorktown, Lexington, Ark Royal, Essex, Bonhomme Richard and others by carrying on the legendary names. The hull numbers aren't passed on to subsequent vessels.
ST's use of 1701-A, B, and so on indicates an honorific to a particular hull number (Constitution class Enterprise only) rather than just the historic name Enterprise.
Is that necessary? Isn't the name Enterprise sufficient? Especially when it's reinforced that the historic tradition extends back centuries to sea-going Enterprise ships, not just starting with the Constitution-class starship.