Why do we need python2.7?

python2 was sunset on January 1, 2020, but in Slackware current python defaults to python2.7

See Quote:

https://www.python.org/doc/sunset-python-2/

In my /usr/bin I see

Quote:

-rwxr-xr-x 1 root root 14392 Feb 13 2021 python2.7* lrwxrwxrwx 1 root root 9 Feb 17 2021 python -> python2.7* lrwxrwxrwx 1 root root 9 Feb 17 2021 python2 -> python2.7* -rwxr-xr-x 1 root root 14392 Aug 31 20:56 python3.9* lrwxrwxrwx 1 root root 9 Oct 4 11:37 python3 -> python3.9*

What still uses python2.7?

What would break if I default to python3.9?

Alex