Honestly, Khaled, that's a tough question to answer. It is all about perception. I started doing karate when I was 14 years old, aikido when I was 36 and this is 12th year in aikido. I have been always been active in karate and only given up teaching 2 years ago: I wasn't convinced that my chief instructor had gained enlightenment to re-invent karate his way.
A hundred years ago karate was a complete art meaning it had grappling, throws and ground fighting beside the hand strikes and kicks but all that changed after the art was introduced into the public school system - it was "water-downed" to make it safe for school children (same for TKD which was a Korean re-invention of JKA style karate). 34 years ago, I thought I have picked the complete art but the only thing missing is a "complete" teacher.
So who are these "martial artists" who only trained in one art?
Peace be with you.
Karate did evolve to a more specialized way with less seizing, grappling, skills.
Non-wushu Shaolin influenced kung fu seems to retain grabbing and joint locks.
Here are some budo thoughts...
"The karate that has been introduced to Tokyo is actually a single part of a larger whole. The fact that those who have learned karate in Tokyo think that it consists only of hand strikes and kicks, and that throws and joint locks are only a part of jujutsu or judo can only be attributed to their lack of awareness on this art. " - Kenwa Mabuni, ca 1925,
In 1924, Kenwa Mabuni and Chojun Miyagi, were asked to take charge of the training sessions, even though they were still fairly young. During these sessions, actual kumite was stressed to increase their physical techniques and strength. It is said that, when a student wanted to learn more from a master, the master would simply invite the student to attack him freely, all the while, blocking and shifting his body while constantly asking the student, "Now, do you understand?" and encouraging them to attack, again and again.
"Conditioning is the greatest hold," and “…A man who neglects gym work is a man who is off balance and without the greatest weapon he can have …--conditioning, " said Karl Gotch, judoka.
The conclusion is that the problem is not aikido or karate, but the advanced karateka or aikidoka and the sensei who loses, or never gain, the martial ("killer*") spirit for sake of the convenient or the "art-ness". In the modern dojo, with all its costs and liability risks, budo must be water-downed to retain a wider range of fee paying students. The challenge is finding a dojo/gym that's alive with sensei (plural) that can also retain advanced karateka or aikidoka who relish punishing, practical, yet compassionate training. *One must be able to have the mindset to kill or be killed, when that's right, into order to cherish and save life.