Most diesel gensets are relatively quiet compared to the big engine, so I doubt the noise complaints stem from that. It's a possibility, though. A related factor is that there is no a/c inside the coach once shore power is disconnected, so running the engine also enables the dash a/c to help. Of course they could start the genset for house a/c and shut off the engine & dash a/c, but many people will say to themselves " it's only a couple minutes more..." If you are conscious of your neighbors, you would shut the engine down and use shore or genset if needed to heat or cool, but if you are one of the self-centered types, maybe not.