Na, I don't think thai boxing is purely for those as want to fight - but that's got nothing to do with gradings. BJJ and judo both have strict grading systems that work perfectly fine. I just dont see what the necessity for them is in a sport that more and more imitates western boxing - which works perfectly fine and does perfectly well financially without gradings.

First way of judging your skill - who have you fought and beaten?

Second - how well do you do at interclubs?

Third - how do you stack up against other people in your gym, and roughly how well does your gym stack up against others?

All simple ways someone can judge their own skill level without having to pay for the privilege of doing techniques that their coaches, if they're being honest, see them doing every training night anyway. Real coaching should ALWAYS be a matter of assessment, evaluation, critique and advice. Given that, the grading system isn't necessary. Making it, in my opinion, wank.