It does strike me that most Gn15 modellers seem to opt for industrial themes, nothing wrong with that but I just wonder why?
Simple one to answer, space and operation.
I would really like to model Eaton Hall, either Eaton terminus or Balderton Junction, but would need to move to a much bigger house to be able to do it properly. If that sort of space was available though, I would probably go for the Ratty instead, not passenger traffic I'm afraid, but the stone working from Beckfoot down to the crusher at Muirthwaite
Even putting aside the location, passenger trains take a lot more space than industrial ones. Even a modest one, say a Heywood loco and 5 coaches is going to be about 4 feet (1200cm) long, so in order to get anything like a reasonable distance to run it in, you are back to a big layout again. A full size train like the ones that now run at either Ravenglass or Romney are going to be even longer.
Just my personnal thoughts why industrial is more popular than passenger carrying lines.