The reason being is that in Thailand, they'd teach you Muay Boran instead if you were looking for its more "traditional" form.
I've read in various places that it's very hard to find a place to learn Muay Boran, even in Thailand. Most schools claim to teach Muay Boran, but they actually teach Muay Thai (or so I've heard).
I mean, in my opinion, it is a traditional martial art...people just changed it to be sport-friendly - like Karate, or other sport-TMA's. I dunno, I'm not too familiar with all of this sport vs real use stuff.
I think most don't give TMA's enough credit. Furthermore most don't look into them deeper than what they see on TV, the Movies, or in the Cage/Ring.
*Nods* Yeah, most people (including myself a while back) thought that if a MA does not work in the ring, it will not work in the streets. Of course, now I'm not such a dunderhead. Lol.
But yeah, JJJ is good for real life use, but I wouldn't really recommend it only because most JJ schools don't have live-sparring - which BJJ schools do. I mean, BJJ isn't ideal for self-defense, but when are you ever going to use "advanced grappling" in a street fight. It's not like BJJ/JJJ masters run around mugging people. Lol.