Only John and Jackie have a reason to be bitter at life.
Jackie quit when he was a millionaire and owned a bunch of properties. He spent his time in semi-retirement telling old jokes and shooting small parts in movies. Jackie wasn't even mad at Howard when he quit as he was already thinking of retiring regardless of the pay. And down the road he got a show on Howard100/101 and eventually did 400 of them when Howard signed to Sirius. So his feud with Howard was not extreme or serious like what happened with John, Artie, Grillo, KC, and a few others.
Jackie quit because he hated doing mornings and was a hippie who wanted to party at nights. Billy quit because he was getting insane offers for voice acting and nothing would have kept him on the show either. They were never going to stay with Stern most likely even if the pay offers were huge. Howard would have needed to basically pay them both 20x what they were making to get them not to just quit. Billy was going to be the voice of movies and cartoon tv shows. Jackie had already planned his retirement and didn't want a long term contract.
John was different.
If they stayed on Stern all these years they’d be 10x as successful than whatever they’re doing now.
John left Stern to become announcer for the Tonight Show. And was making over $300K per year. He was more successful after Stern than before. John just pissed away all of his money and show business connections for whatever reason. Which is more successful? The guy who asks mean questions and ambushes celebrities for 80K a year with no chance of promotion? Or the announcer of the Tonight Show who makes $300K and has access to A-list celebrities and producers 24/7 and can network in Hollywood?
We know why Leno signed John. Just to piss off Howard. John kept getting calls from reality tv producers to be a guest on various shows. And to be a guest on various late night talk shows to promote his gigs or whatever. And Howard said "no...they just want you for free plugs on my show and my airtime" over and over to prevent Stuttering John from getting gigs. Somehow word of this got to Leno and he decided to hire John for the first open position on his show.....which happened to be the announcer. For a guy with a vicious stutter. Leno did it because he wanted to piss of Stern and didn't really look into what kind of talents John had besides celebrity interviews. As Leno was a loser who hid in the closet to steal the Tonight Show from Letterman and didn't really survive on talent and got his career more on backstabbing.
The NBC executive for the Tonight Show was this guy Rick Ludwin. His only jobs at NBC were to manage the Tonight Show and Seinfeld. When Leno told him he wanted Stuttering John from Stern to be his announcer he thought it was a joke at first. Then pleaded with Leno not to do it. But Leno went through with it because he wanted to get Stern upset. Which worked as Stern's dream was to host a late night talk show like the Tonight Show. This was a big loud signal that Stern was beneath the Tonight Show who could poach his guys for a laugh.
But this was the funniest part. Leno's writers and producers didn't listen to Stern. And neither did Leno. They listened to other shows or their own music in the mornings. None of them were familiar with Stern at all. So they all thought, including Leno and Ludwin, that Stuttering John wrote all of his own material and wrote his own celebrity ambush questions. They had no idea that Jackie, Fred, Howard, and others were the actual writers. So they impulsively sign John to a huge multi-year contract as 'announcer' but tell him on the first day 'you also have to write your own material'. Well John says "I never wrote anything before.....Jackie or Fred wrote my stuff". Leno hears this and flips out realizing that he just hired a useless moron.
John would eventually be taken from the announcer position and put into the writers' room. But this was just him being phased out until being fired by NBC. Yet Leno kept his word and kept John on the Tonight Show, even letting him announce and do bits and skits, and on NBC until he left the network himself in 2014. Leno told John that he would have a job at NBC until Leno left the company at which point NBC would most likely immediately terminate him. John turned that loyalty into being a taxi driver and substitute teacher apparently and losing all of his money in the divorce.
