Sr. is pretty delusional, but you never know what they "choose" to air. However, he does give them a lot of material that makes him look bad. And yes, it was convenient for Sr. to drive over to Paulie's shop, however, it's not as staged as people think. Camera crews follow each of them ALL day. At the end of the day they send around 15 tapes over night to the editing crew in LA. There is nothing that isn't filmed during a day for them. When one of them goes on a ride, a truck with the crew follows them with 4 people harnessed in the back of the truck with steady cams. So if Sr. drove over to Paulie's shop, he could stop, all four of them jump out of the truck, and you have an instant crew for an interview. Sr. just has an ultimate ego and believes that nothing can be done without him. Vinnie never really stated why he left, but I think he got tired of the BS involved with the shop. In the earlier years Sr. used to get on Vinnie just like Paulie. At one time he even made Vinnie in charge of cleaning up the shop, regardless if it was his mess, and would send him home early if it wasn't clean. And Paulie appears to be lazy at times, but in the early seasons it was him and Vinnie at the shop at 2 AM working on bikes and no one else.
For those interested:
When the show started filming Jr. was just getting his shop started. However, prior to Sturgis he built two bikes three weeks. One of which is Geico, which is being used/will be used in their TV commercials for the motorcycle insurance. The bike looks pretty great. Much better than the recent OCC stuff. His other bike is a web themed bike called "Anti Venom". I wouldn't be surprised if the next season only has Jr's shop and no OCC.