Aside from the dross that gets churned out on the JPP chat, I actually feel it's a very clever thing they have going on there.
Some people like to gamble alone, it's their own time and own space. A lot more people like to gamble in company. Take the atmosphere of a buzzing Blackjack table in a live casino - good dealer, nice set of lively players, maybe throw in a deck that's running hot for most people, you just can't buy that entertainment alone. It's a great buzz, and brings gambling a little closer to what it should be, fun.
Now a chat window is not going to get anywhere close, but I have had some pretty good conversations on there when there right mix of people are online. Whether it be banter, or a more serious topic. I repeat again, you just have to filter out the crap mentally, or use it as entertainment.
It's not quite as bad as a bingo site - you don't see that much lucky dust to be fair, or that kind of multi-coloured text with half-ass drawn poor pixies and mountains of coins.
The site does well to tolerate all the people who moan and moan - it could be construed as a bad advert for them all the negativity, but very little is censored in that regard, but they do come down on you for serious infractions of etiquette or politeness. However they really need to sort out their chat filter that is over zealous to say the least.
If I log on to JPP and bump into a few respected fellow players, then I'll want to say hi and have a quick chat on the state of gambling affairs. That's a draw for me, I think other sites would do well to follow suit on more social interaction.
You will always get the cyber beggars, the cyber moaners, that's human nature - frustration at losses needs an avenue to be vented and if it's the alternative to chucking the laptop down the stairs, then the chat box is a good thing.
I only recently opened up the 3Dice chat client, and to be fair, very little is said on there by way of conversation - you don't get as much dross, but it got a little irksome that the chat window is constantly filled up with slot tournament winners rather than a good conversation to follow or join in with. Maybe I hit a couple of slow days in there, who knows.
Anyway, in summary I think some people need the chat box, to feel closer maybe to other people and gain some sense of community that takes the 'on your own' feeling away from the physical environment you may be playing in. I regard it as an extra avenue of gaming experience that the lesser initiated who have no concept of how RTP's and RNG's work utilise as a social enhancer to a possibly anti-social pastime. Maybe, you're like me and use the chat sparingly, but like the option to let people know you're out there.
We all know it's sickly sweet, the big bad money making machine is hiding behind it all, just waiting to pound your wallet good and proper, regardless of the bells and whistles that are implemented on the journey to succeed in that aim, but if I can tip my cyber hat to a comrade in the trenches, or congratulate the person who just hit the 4 star progressive, or even take part in the quiz, then it's going to make me want to come back for more.
- self excluded myself for 6 months and occasionally play the same games at 
