Seriously though, the issue here isn't that 'groin attacks never work', it's that relying on a single 'fight ending' blow is not good s.d. training imo. A lot of techniques I've seen in krav involve a pulled kick to the groin and the person playing attacker acting as though they are really injured, bending down, whatever, so that the technique chain can be finished. I'm not saying that krav maga wouldn't have a response to missing the groin, or the groin attack not actually doing anything, just that what is out there doesn't show this reality. Considering krav's claim to fame is RBSD, I find this odd.
Perhaps we are missing the point. Perhaps the reality is not a fighting ending blow. But a blow good enough to make an escape and end the fight that way. For someone who is a non martial artist a basic self defense clan can be predicated on such techniques good enough for escapes. Single attacking techniques delivered to an opponent by surprised not meant to maim or kill but good enough to enough to make a quick get away.
Later on a more advance course in self defense can carry on the basic attacks and lead into the realm of "what would you do if the person blocked the attack." Then you can go into follow ups and address the "what if's?"
Neither boxing or MT training is predicated on a single fight ending blow. That is the goal, sure, but techniques are taught in a manner where if that blow is unsuccesful, you can launch the next one. If fight ending blows were so easy to attain, I hardly think either of these arts would be interesting spectator sports--they would be over in seconds.
That's why they are sports. Because it's based on continuous combat separated by weight classes to make things as equal as possible.
So one question I have is...why does a MT match often take so long to acheive a knock out (if it indeed does), whereas RBSD systems show the fight ending in seconds? Which one is more realistic? Is the truth somewhere inbetween?
MT is a sport and while they go full contact and fight hard. They are not in real life or death combat or at least that is not the goal. Rules, weight classes, and most importantly the element of surprise has been taken away.
In RBSD both fighters being equal in attributes and skill, it is the one who cheats first using the element of surprise who will be the victor.
Basically, all I'm saying is to check the assumptions that go into techniques. If the assumption of your technique is that this one blow will 'finish' your opponent, well, I don't think that's so good. If it's 'this might do this, but if not here's how to flow into something else', then that's good.
I agree you can never go in believing one technique will end the fight. You can only attack and see how it goes. I wouldn't recommend stopping with one attack until you know you can get away.