It's been explained to me by more than one very experienced Krav Maga instructor, that the self-defense "scenarios" that KM employs were systematically arrived at by reviewing hours of videos and eye-witness accounts to street violence. After sifting through this information, the highest percentage attacks were obvious, and the original developers knew what to start working on.
In other words, the most common street assaults were boiled down scientifically and statistically, which informed the creators of KM, from Imi Lichtenfeld downward, what to spend all their time on. Rather than saying "let's come up with an interesting defense to a cross-side, upside down 45-degree thumbless grip", the data told them that that kind of threat may have only occurred (unfortunately, I've not seen the actual findings) only .003 percent of the time, so it was almost useless to address that type of attack. That's why, as Krav Maga students, we train on only about twenty major scenarios, instead of countless, endlessly more imaginative ones.
The information also provided, obviously, the most commonly faced situations: frontal chokes, headlocks, bear hugs; in short, the staple techniques taught in every KM school in the world. These are the situations or "scenarios" that are addressed the most in Krav Maga because they happen the most in real-life, human to human encounters.
Speaking for myself, I use the following concept as a teaching model: "scenarios" can be split into two major sections: the initial response, and the follow-up - which are called "combatives" in KM terminology.
I like to split it into two sections to be easier for beginners (and sometimes, even more advanced students) to digest.
If the first part (initial reaction) is not effective, everything that comes after that is not very important. For instance, take the scenario "Choke Against Wall From Behind." This scenario assumes that you don't find yourself suddenly smushed against a wall; you're standing a step or two away from it. An attacker rams you, face-first, into a wall, or car, or ATM that you're standing in front of.
The first, and most important, thing taught in this scenario is to turn your face and slap your forearms and palms into the wall in order to save your skull from being smashed. I call the arm motion "goal posts" to help students visualize and remember. After this, you spin and go into some cool combatives.
Everyone loves combatives.
I think you'd agree that if you don't turn your face, if you don't absorb all that explosive forward motion - including all your body weight and his - that everything after that doesn't matter much. You are, most likely, partially asleep, bleeding from a nose which now takes up more of your face than it once did, in a heap on the ground - not exactly the best state to execute terrifying hammerfists, elbows and knees from.
That first reaction is important. So important that many instructors make it a point to isolate that first motion repetitively before ever allowing you to begin counterstriking. That's why so much emphasis is placed on plucking correctly, or basing out correctly, or spearing correctly. You may be in a hurry to deliver that awesome flurry of unstoppable knees, elbows, and groin shots... but unless you actually make them stop strangling you first, you may not have a chance to impress them with your overlapping counters that inspire fear in tombstone pads far-and-wide.
The second part of the scenario comes second for a reason.
So take time developing those initial responses, and have confidence that a lot of statistical work has gone into the why's and how's of what you're doing.