Most people don't want anything they like to be diluted or changed. People on HN don't want people from Reddit. People from Reddit don't want people from Facebook. People from Facebook don't want their parents. People in a gated community don't want poor people moving into their neighborhood. People in the city don't want rich folks moving in and gentrifying their block.

People, in general, are xenophobic and like their culture to stay small and untainted. Eternal September happens everywhere. It doesn't mean that Google has to keep two separate mapping applications running. Waze didn't stop to think about their community when they sold the application to Google.