You could give the article a read? I think I lay out quite clearly why they are such interesting languages, but if you have any questions feel free to shout here and I'll do my best to answer.

Just on the age thing - linguistic innovation doesn't need to be long term to be interesting, in fact, the rapid development of a new language is really fascinating both in what it says about how language works and also what we can learn about humans more generally. Some of the most interesting linguistic innovations in 'older' languages were rapid, two examples from English that spring to mind are the extreme loss of morphology between Old and Middle English, which occurred over a couple of hundred years at most; and the great vowel shift, responsible for much of our spelling irregularity in English which happened over just a couple of generations.