Bottom line is that most people don't have, or don't want, 8 years to study martial arts. They want something that will be effective and implementable as soon as possible. And I think Krav Maga fits the bill pretty damn well.
That is a very interesting perspective. I think it's a combination of this and marketing. Krav Maga is a very recognizable name, and it's billed as fitting this need. I also think that because it comes from a military background, it's seen as more effective than other systems.
I hadn't intended to be quite so specific to my chosen style, but also to other styles/systems that I've checked out. For example, JKD, which gets right to the meat and potatoes of things, or even certain styles of jiu-jitsu.
I'll be the first to admit there is plenty of esoteric material in a lot of Kali systems that is not essential to fighting.