Those who are content with abstract hit points don't need a more elaborate wound tracking system. Adding such a system for everyone is an unnecessary complication.
That's not to reduce it's usefulness to those who do want such a system.
But the simplicity of the hit point mechanic shouldn't be casually discarded without a clear idea of the desired result. While abstract hp lack the detail some people obviously crave, they have served D&D well for decades, and are sufficient for most games IMO.
A more complex system will need extensive testing to shake out any bugs and discover and deal with any unintended side effects. And it will need to be strictly optional.
Right. The game designers have to create a game that attracts new players AND maintain old ones. New players (and lapsed players who return) are going to play the 'default' game and they are going to come at it with an expectation of a hit point model that matches what they have experienced in pretty much any other popular game (a character is alive and once it sustains a certain amount of damage it is dead). They will look at systems that simulate wounds or have extended healing times as punishment for participating.
Experienced players such as Derren who want something a bit more robust will house rule to suit their needs or pick up optional systems suggested in the core books.