This is very true. The places that have a sense of community make it more likely folks come back - they miss the people more. My primary instructor really wanted a sense of community, but wasn't very good at fostering it. I know another NGA guy who has cookouts and gatherings for his folks. His retention was always better.I don't worry until 2 weeks go by. I try to build bonds with people so that they have other reasons to show up for martial arts. The company that we keep plays a deep role as to who comes back after a long time.
If those relationships aren't there then it's easier to walk away. When I go missing people ask about me. When they go missing and come back always tell them it's good to see them again.
poetically speaking, warriors on the same path is a good feeling to be around.