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 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.
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.
Visible crew/equipment: When Beetlejuice is first introduced, right before we see him, the camera rotates around the model and the sign above the grave lights up. Right before the sign lights up, you can ever-so-subtly see a part of the camera's shadow move over the model. It's subtle and easy to miss, but once you see it, it's pretty obvious.
Revealing mistake: When Wolf Jackson touches a headstone as he and the police are about to raid the church, you can see the headstone wobble when his hand lightly touches it, revealing it to be made of a soft, perhaps Styrofoam-like material and not a real headstone.
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.