User blog comment:Martialmaniac/Hisoka's tattoo/@comment-1220514-20160315121754

Hisoka is the wild card. Togashi probably doesn't even know why he does things.

I think you're bang on, though. Hisoka didn't even attend the scheduled meetings, only going when he was told he could be kicked out and thus lose his connection to Chrollo (because when he's good at not being found, like Ging). Hisoka doing it for the thrill too also makes sense - he made his own prediction on the spot and just hoped they wouldn't figure out he's full of it. He even told part of the truth, which could have gotten him killed for leaking info about the Troupe.

It's possible he also did it as a challenge - "how long can i pretend to be a troupe member for?" As he is someone so clearly unconventional, just chillin until Gon's old enough to fight seriously, he has to do something to stop being so bored.