What are some reasons we leave Drupal, the software? What do we leave it for? What does this say about Drupal, the software?

What leads us to walk away from Drupal, the ecosystem/community? Where do we go, after we leave? What does this say about Drupal, the community?

Are these all necessarily bad things?

As we continue to evolve Drupal with an eye towards bringing in new contributors, how do we retain those already in the ecosystem, even as technology, communities, careers, lives, technologies and trends change?