The flippant side of me wants to say "decades of experience". As I said in the bit you quoted, "all special effect system falls down under its own weight".
I'd concur with this.
Pure status based systems tend to bog down in mind numbing complexity, particularly since they are driven by the desire to achieve 'greater realism' and typically keep finding themselves not meeting this goal in practice - which the designers typically try to address with even greater complexity.
Essentially, each wound becomes a debuff. Buffing and debuffing is the single most complex and frustrating thing about the D&D play experience, and you would have a system were every single hit led to a debuff.
So you have the same problems with resolving buff stacking as D&D has in spades. For example:
1) Suppose you take a minor wound to the leg, hense -1 Dex or maybe -5 to movement rate. Now, should or should not a minor wound to the arm stack with this? What about a second minor wound to the leg? What about a third? A tenth? You end up with essentially tons of named bonuses which must be compared with each other.
2) How many minor wounds does it take before you escalate to a moderate wound? If the answer is non zero, then you can be scratched to death by the most trivial of causes. If the answer is zero, then you can be a mass of hundreds of cuts and bruises and still be no more wounded than the guy who has only one scratch.
3) How do you deal with the anticlimatic death spiral, where each wound tends to make it increasingly unlikely that the fight isn't going to be completely one sided? Aren't you in fact going to make magical healing even more important if you want a fast paced game??
And what is combat like when everyone is walking around with 12 debuffs that they have to add to their calculations? And if not 12 debuffs because wounds are rare, how do you deal with the fact that the player feels like he has no control over the fate of his character because he's always one unlucky roll from death.
Quite often you add lots of extra complexity to no net purpose. Maybe you could get a computer to handle it, but I notice all or virtually all computer games use hit points rather than any of the more complex systems that sometimes show up in PnP.
I've had the same adding complexity to no effect problem with implementing called shots in my game. It seems like there are circumstances where this would make sense that you could target a specific thing, but what you find is that its very hard to deal with two issues. The first is that it's very hard to have a system where called shots are a reasonable option, and not yet an obviously better tactic than not making a called shot. Typically, called shots will either be so inefficient of a tactic that they are never or almost never worth it (in which case the extra complexity probably isn't worth it), or else they are used in every attack and the net effect is exactly the same as if you reduced every ones AC and/or hit points by some amount. The second problem with called shots is that you now have the additional complexity of dealing with what a 'miss' means. If I call a shot on the elephants head, I could have missed it, or I could have hit another part of the body. Without some way of tracking how I missed, I have no way of knowing. Unless you want to implement the complexities of something like 'Aces and Eights', the system probably won't actually feel more realistic.
You could offer a system where each player chooses specific tactics against a matrix that determines result, with the same problems, as well as (probably) a far slower combat resolution.
You could offer a system where choice of tactic instead causes a penalty to the attack roll, and causes the special effect when successful....but then why would one not choose "Kill my opponent" (or the closest thing thereunto) every time?
Answer: Because 'render my opponent helpless' is such a comparitively easy option in the system that I should chose that tactic every time. For example, if the system makes crippling an opponent so that they can't move very easy, then the default tactic will be cutting the legs out from under the foe and then finishing them off at range. Or if the system makes cutting off the opponent's hands so that they can't attack too easy, then the right tactic is always doing that first and then finishing them off at your leisure.
In short, while I cannot rule out the possibility of a great non-hit point combat system, I have yet to see one that works as well.
The only alternative to hit points I've seen work well is a damage track where each wound produces the same abstract consequence. That in my experience tends to work well for games that lie to either side of D&D's sweet spot - either grimmer and grittier or else more cartoonish. But on the whole, I find that hit points are indeed the worst system ever except for every alternative. Back in my naive days when I had only limited experience of systems other than D&D, I used to blast D&D's lack of 'realism' as well.
Not so much after 25 years of gaming.
