Those type skills require a certain youth, and constant training, while the relaxed and reactive circular parrying and locking and throwing styles like Aikido are effective years after training, even when older. They become relexive, so that an unexpected attack (a sucker punch) is dealt with from deep instinctive memory without warming up, stretching, getting into a stance and so on.
Plus, against mulitple opponents, Aikido is much less energy draining. High output styles like TKD leave one quickly exhausted when facing multiple opponents who are cagey in their attacks.
Just MHO, your mileage may vary.
Not to mention that the kicks are only effective at the optimal turning radius or distance. I've been studying about 5 years, first in tkd and gracie jujitsu, more recently in tai chi.
Tai chi and akido are both "internal;"they train timing and balance over strength and technique. It takes much longer to learn these techniques, but they can be assimilated into harder styles. Young students should probably learn basic self defense first anyway; scars and krav maga are both effective distillations.
Why do I like internal arts? They teach you to keep your head. Many assaults, or invasions, are not physical;it's usually about someone crowding you out or trying to intimidate. I think the internal arts sensitize a person ,psychologically as well as physically, to both kinds of insult. One last thing: these arts are more "literate;" they've been around longer and have been extensively documented. That sort of thing becomes important once you round 40 and your knees start to creak.
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I'll offer a bot of advice from someone who has been places he wishs he never been and seen things he wishes he never seen. There have been times I've wondered if I'm fit to associate with decent people because of it.
The business of a 98 pound weakling defeating a 200 pound man by using his own strength against him with Asian arts is a myth that will get you killed in a serious situation. If you are going to get in a tussle with the big boys, particularly if the have knives, clubs, or whatever, you need to be able to move fast and deliver a single incapacitating blow. That takes STRENGTH and training. I know how to break a person's spine, neck, or arm if he grabs me. I know a few nerve holds. None of these are generally known to the average person. The moves are not particularly taxing. They require speed. They require more force than you might expect. Those two factors are the result of power training. There's no substitute for it.