Nephilim, thats the point- not everyone is arsed about fighting, some people just choose a martial art and do it because they enjoy it, be it tkd, karate, kung fu, jun fan, silat, caporaira, jui-jit-su whatever!
i completely agree that when you pitch a tkd guy against a muay thai guy, 9 times out of 10 the thai guy will win because thai boxing is all encompasing, and yes, if your sole aim is to compete then it stands to reason that you want an art/sport that teaches you to guard your head and kick the legs!!! But even if you decide to compete in tkd, your not gonna think to yourself "oh shit, i dont guard my head, what if i have to fight a thai guy" because tkd guys just compete against each other in those rules (with the odd exception as above).
clearly the problem is people not doing their research (based on what they want from a martial art) before they start. perhaps if people had looked into the arts more thoroughly before they began they wouldnt have wasted their time training something that couldnt help them reach their personal goals.
it doesnt make the art they chose any less valid, it just means they wasted time doing something that obviously wasn't right for them. but you only have to look at the hundreds of thousands of people that do train in tkd karate etc, in comparison to the amount of people that train muay thai to see that they gain from it, whatever that gain may be.