The big question is "What is your idea of the ideal sim world?" Most people would play for either the features of the world or the scenery. some people like the seaside, some people like the country, some people like the mountains. I would suspect that people change neighborhoods because sometimes they feel like playing in a big city and sometimes they play in a small town.
Also, sometimes people might watch a movie or a TV show, like Dark Shadows, and want to play in a spooky seaside New England town or wherever the movie or TV show is in.
Most the time, I play in Alfredsborogh or Prosperity Point. Both of them have the lots I want, and Prosperity Point has that early 20th century look. It would be fun to have enough in game clothes to play a city or town from it's founding to present day, though every few generations you'd have to bring in new families so everyone isn't related.