I can only speak for myself & the knowledge I've gained over the years of training Martial Arts.
Someone here said that in boxing, Krav Maga, etc; there aren't that much techniques for you to learn, which I agree with.
I have boxed, I have observed attentively the techniques of Krav Maga & what all these sports or fighting techniques have in common is this: lack of variety in different fields of energy.
What I mean by that, is all of those techniques mostly require force & strength. They are explosive; which doesn't really require the same skills as Martial Arts does.
I have found that it is MUCH easier for me to revert to an explosive technique built upon strength, than to transform all of my energy into kata that requires me to move like the wind, the earth, fire, & water.
Most Martial Arts kata requires you to move based on the different elements (mentioned above). It requires you to shift ALL of your energy into a specific element; & actually perfecting a technique like that is what takes so much time. Why? Because we don't live in those different states of energy on a daily basis. From the day you were born, you've only grown accustomed to ONE state of energy, & to now transform that energy you've lived with your entire life into other states of energy; THAT is where the struggle, the time, & the effort comes into play.
If I had to compare myself to my Sensei, there would be NO comparison. He can tranform his void energy into any other element, & one would not notice the shift in his energy, only in his kata. Why? Because he's been doing it for YEARS. THIS is where the "mastery" concept comes into play.
Martial Arts is all about energy, & connecting to your higher self. It's about the vibration of the atoms in your body & tuning into those vibrations.
This is why beginners will practice kata in steps, rather than in a flowing motion. Or they will do the kata, & then pause, disrupting the energy they started with - they are not used to it. They continue to shut the element's energy off, & revert back to the energy they're used to.
I don't know if all Martial Arts divisions requires you to shift into the different elements, but Ninjutsu does.
It's the only way I can put it into words for you.