In some of the oldest D&D adventures (mostly pre-AD&D, I believe), there were instances where attacks or traps would do limb damage/severing but as the game got more and more codified, that seemed to go away. All instances I remember seeing were codified in the module (or monster) and never in the core rules. I knew several tables who used the negative hit point system would often have characters returning from such states with grievous wounds or limb loss.
Likewise, a lot of systems separate Hit/Luck points from a smaller pool of Wound points (Palladium was where I remember first seeing it, SAGA Star Wars probably the best defined that I remember). Even D&D style video games have done this separation poorly - how many of of us have played the likes of Minecraft with half a dozen arrows stuck in the character as they continue to run around unimpeded? Bloodied is probably the best D&D has done to separate the luck/scratches a character receives vs. a telling blow, but even that is more abstract than it should be. Implementing such a system though would require a lot of deep changes and monster rewrites, I believe.
Personally, I don't ever equate hp loss to "meat", especially after Gygax's article on the subject.*
All the way to the early days of D&D, there have been magic items that hint at limb loss being possible - Vecna's hand/eye replacement, Teeth of Dahlver-Nah replacing your own, Vorpal and Sharpness swords cutting off limbs, etc.
While limb loss is certainly a downer, I would certainly like to see D&D embrace an optional system that accounts for the chance of such grievous wounds - opening up a host of options for mundane items, spells, magic items and more.
Actually having an in-game reason why your character is wearing an eyepatch or has a peg leg, players nodding sagely when such an injured NPC warns them about "look what the beast did to me!" and mean it I believe would enhance the simulation side of the game (and the fear of a similar loss).
Such loss need not be so grievous that players instantly retire a character that suffers such a loss, but they should have at least some mechanical effect - as well as be a badge of honor of just how
tough such characters are to have taken such a wound and soldier on regardless.
In the end, I think that is a lot of what this whole thread is about - repercussions and effects that matter beyond a short dip in hit points or a short-term status condition.
*
Gygax said:
Hit points are a combination of actual physical constitution, skill at the avoidance of taking real physical damage, luck and/or magical or divine factors. Ten points of damage dealt to a rhino indicated a considerable wound, while the same damage sustained by the 8th level fighter indicates a near miss, a slight wound, and a bit of luck used up, a bit of fatigue piling up against his or her skill at avoiding the fatal cut or thrust. So even when a hit is scored in melee combat, it is more often than not a grazing blow, a scratch, a mere light wound which would have been fatal (or nearly so) to a lesser mortal. If sufficient numbers of such wounds accrue to the character, however, stamina, skill, and luck will eventually run out, and an attack will strike home...