Either you are deliberately choosing to insist you don't understand me, or I have exhausted every way I can think of to communicate to you and failed to do so successfully.
As you were so intent on pointing out, the explanation you find the most obvious isn't necessarily the only one.
"blamed" for as that, to me, implies fault or wrongdoing on their part which is why I said I wasn't blaming the players before
So, you're not 'blaming' the players, you're just attributing the problem to them, rather than the system. Distinction noted. Judged meaningless, pedantic, and evasive, but noted.
Expectation of when and how a PC will arrive at 0 hit points.
You mean like "in combat" and "from enemies trying to kill them?" Pretty realistic expectations, for adventurers.
I mean, traps & hazards are also in the offing in most D&D games, and its certainly true that healing an ally who fell in a pit just doesn't have the same 'whack-a-mole' feel to it (perhaps ironically, because he /is/ in a hole).
Doesn't seem like a very meaningful insight, though, thanks just the same.
For those of us not intimately familiar with the healing rules of previous editions, and still wanting to contribute to this discussion, how does the "heal-from-zero" become an issue?
...Is it simply that if a player who had 30 hp was hit for 38, reducing them to -8, can now be healed for the full value of a spell? So healing word which rolls 6, brings them to 6 hp instead of -2... which honestly seems like a waste of time to me, since they'd still be bleeding out and dying and your action was to do nothing to change that circumstance.
Yep. Heal-from-0 means it's never a waste to heal a fallen ally, and that waiting for the ally to fall 'saves' you from healing the damage he took over what was required to bring him up to 0.
In past editions we tracked negative hps, so if you were reduced to -8, you needed 8 points of healing just to get back to 0, and more to get up to full. So if you had, say, 12 hps and were hit for 10, then another 10, you'd be reduced to -8, and need all 20 hps you took healed to get back up to full. Not only that, but there might be serious consequences to being reduced to 0. So, it was a good idea to heal an ally as soon as he'd taken enough damage that you could use a spell without 'wasting' it. In the above example, you might cast CLW (1d8) as soon as your ally took those first 10 hps of damage, so he could take the second hit and still be up, he'd still need 12 more to get back to full, the same 20 as if you watched him get beaten down before doing anything, no upside to watching your friend dying.
But, in 5e, if you waited for him to drop, you'd only need to heal him for 12 hps instead of 20. Saving healing resources. An upside to dying.
So... I am confused to a large degree of the nature of this problem.
For some of us, the problem isn't a big problem - so it's efficient to let your friends nearly die before you bust out the healing - it's not like D&D is a paragon of realism and genre fidelity, anyway, do what works best. For others, it's annoying, and a fix is desirable - the OP wants to fix the issue, mechanically, rather than work within or ignore it.
Some of the possible solutions, like death at -10, are just turning back the clock to a previous edition that didn't have the problem.