Going by the book for an animal companion is what you do when the Beastmaster can't get a companion any other way - it is a class feature under player control.
Normally as you say, you can just Awaken/Animal Friendship, buy or otherwise treat your pet as an NPC. But then your Ranger Beastmaster features don't kick in and ultimately it is under the DMs control even if it normally gets directed by the player.
My issue with many Beastmaster fixes is that the player wants the DPR of the Hunter subclass (which is nearly all the Hunter gets) and then ignores the added exploration and versatility that the companion adds.
The Designers usually describe the ranger options as Attack power (Hunter) or Versatility (Beastmaster).
It also helps if the DM doesn't get hung up on 0 HP = Dead, because nothing in the rules requires that. They get Death Saves, HD short rest healing, and overnight full recovery plus reactions and OAs.