I'm not saying it's impossible to end a confrontation with one well-executed technique (that it is possible has been proven time and time again), I'm just saying that it's not a fighter's philosophy. I've dropped people (and been dropped) with a single shot, but normally it takes an accumulation of effective techniques to wear your opponent down. If you practice every technique like it's a potentially fight ending blow, when you have to "go", you will use hard, fast techniques. If you practice like "this won't take him out, but I'll do it half-heartedly anyway", your technique won't do anything but open you up for a counterattack. You have to strike with "bad intentions".
Wearing padded gloves, as in boxing, changes a lot. If boxing were bare-knuckle, they would probably put more emphasis on defense and less on winning through attrition. Even with the gloves, they don't teach weak punches, although a distinction is made between jabs and "power" punches (a good, solid jab can be quite effective in it's own right).
It doesn't matter if it takes one, or one hundred techniques to eliminate a threat, you'd better be prepared to go the distance.