Maybe it's the fact "python" usually runs Python 2.7 on modern systems. From there, you use the built-in documentation, learn your way around the language, and

Maybe it's the fact "python" usually runs Python 2.7 on modern systems. From there, you use the built-in documentation, learn your way around the language, and end up with Python 2.7 as your daily driver. You have to know to write "python3" to get Python 3. In effect, it's not the default, it's the special alternate version.