Continuity mistake: When Lydia first meets Delia, there's a man in the glass box behind her walking around. Between cuts, he suddenly moves back about five feet.
Continuity mistake: When Lydia introduces the guests on her show at the start of the movie, the way the woman is holding her dog "Taco" changes between cuts. (The dog goes from facing Lydia to facing away between cuts.) This sort of mistake happens several more times over the scene.
Continuity mistake: When Astrid walks into her dorm room and the ghost swings down, we see her laptop is open and dark on the desk. When she continues to enter the room and approaches her desk to put her stuff down, the laptop is now lit up and unlocked.
Continuity mistake: When Delores is stapling herself back together, she's seen putting 7 staples in her face from her upper lip to her forehead. When she's going to attach her ear, there's now over a dozen. As the rest of her reconnects, there's now well over 20, and we do not see her adding any to what was there.
Continuity mistake: When Rory finds Lydia's pills and says "No," Lydia's mouth goes from closed to open between cuts.
Continuity mistake: When Rory is first seen at the studio, suddenly an extra production assistant appears behind him when it cuts from the medium shot to the extreme wide shot.
Answer: Why are most people so intent on marrying someone? He loves Lydia. In the first movie, she was a teenager, and he mostly needed a wedding to get out of his punishment. In the years since, he appears to have developed more respect and appreciation for her. He stopped her wedding to Roy, exposed Roy's fraud, and transformed their almost-wedding into the smaller, "private" ceremony that she really wanted. He doesn't want to "just find someone else" for the same reasons that many people don't.