For anything non-trivial, 95% of the value is in the library ecosystem. So long as most prominent libraries kept releasing new features for Python 2 and 3, ther

For anything non-trivial, 95% of the value is in the library ecosystem. So long as most prominent libraries kept releasing new features for Python 2 and 3, there's inevitably not a big pull factor to upgrade. That's changing as a number of major libraries start to make releases that require Python 3. From a library maintainer POV, I do want to use Python 3. There's no one killer feature, but rather a bunch of small ones, like more specific exception classes (FileNotFoundError etc.). But if you want to keep using Python 2.7, no-one will take it away from you.