I was talking about major Linux distributions like in the first 3 or 4 (I don't want to dismiss Arch, but this more of an expert distribution than a major/popular one). Obviously, there are a lot of Linux distributions today, however most people will use some flavour of Debian, Ubuntu or RedHat.

I think a number of distros include python3 by default, but -- per python's own standards (adopted as a result of disruption caused by Arch having python3 as /usr/bin/python -- it isn't linked to /usr/bin/python but to /usr/bin/python3; /usr/bin/python is (except on Arch) always python2. That's not a matter of which is "default python" (e.g., even if, as Ubuntu plans to, python3 is the only python installed (not merely "the default python"), it will only be /usr/bin/python3, not /usr/bin/python.)

This is about consistency given that major versions aren't intended to be backward compatible so scripts either fail or find a compatible python when using a shebang, not about what is "default".