Karate is a very subtle art with focus more on aspects that cannot readily be discerned; this effectively removes it from the realm of combat as most who wish to learn would expect to learn something they can use right away.
Certainly one can gain this from Karate, but as a whole Karate is the long way, there are other things out there a person could study that do not take near as long to understand in order to apply and many of them are able to be directly applied.
That is not the point of Karate, the point is much deeper... Will Karate work? Yes. Again, is that the point? No.
Karate is a core focus that can and should be applied to everything, from cooking and cleaning, to sports, to the way one behaves and, finally, to combat.
If that is the main focus why would a person look at the mechanics of a single punch, or posture, in Sanchin Kata, or the rotational aspects of Seipai??
These things are training tools and meant to focus on different things that can carry over to combat.
The focus many have on Karate is strictly as a Martial Art, or a Civil Defense Art, the latter certainly applies, but they get stuck here, they begin to identify as what they are doing rather than looking at it as something they do to improve themselves, to ground themselves.
The idea is not to limit oneself to a certain thing or a certain identity or to limit what one is doing to a specific focus, but to allow it to exist as it is and allow it to do the work it is meant to do.
At the same time a deeper aspect is to unify with it, to become the center, the dancer and the dance, while at the same time not identifying AS the thing or as SEPARATE from the thing.
Internalizing what you are doing will come out when thought ceases, when expectations cease, when everything is allowed to fall into place rather than forcing something to do a specific thing you think it should be doing... That is like trying to pound a square block into a round hole.
These days Brazilian Jujitsu and Muay Thai are very popular through MMA Training, trends come and go because people have these expectations and these are not wrong, but they do show a lack of depth as one thing comes and another goes.
Enrollment in Karate is at a low in some areas, a high in others... At what used to be our Hombu Dojo Karate is no longer the main attraction, most go for Judo, Jujitsu, and MMA type stuff, these things pay the bills while Karate exists as an aside, which is a much better way for it to exist because it is allowed to be what it is meant to be rather than a means of keeping Students walking in the door in order to pay the Dojo bills.
Karate is a path of peace and self cultivation... You study the kick and punch in order to understand the hug and handshake, to shut conflict down before it even starts while at the same time you have the tools to deal with things should confrontation be the only possible option.
This is not just Physical Conflict, this is all aspects of Conflict, and this is certainly lacking in many Dojo these days, but it takes more than just physical conditioning and skill, it is mostly a mental thing.