On Fedora, there's a line in /etc/skel/.bash_profile that adds ~/.local/bin to the default PATH. Debian doesn't have an equivalent.
I just filed #820856 to hopefully get this added to Debian. (It's possible that in the mean time pip might need to grow some logic to check whether the user's PATH is correct, and even offer to fix it up by appending something to the user's ~/.something. This is a pretty significant stumbling block for new users, and even if Debian fixes this today then it will take quite some time for the change to propagate out... esp. if the fix goes into /etc/skel, because in that case existing installations will *never* get the fix, only new ones will.) -- Nathaniel J. Smith -- https://vorpus.org