Managing multiple Python installations in PATH is problematic, so by default the installer doesn't modify PATH. Instead, the "py.exe" launcher [1] is made available, which can run any registered installation of Python. 

Using a launcher fits the Windows environment better, which installs applications into separate subdirectories of "shell:ProgramFiles" or "shell:UserProgramFiles". This is similar to monolithic package installation in Unix into "/opt" or "~/.local/opt" (or "~/opt"). 

A recent update to the installer extends the message after a successful installation to suggest "[a]t your terminal, type 'py' to launch Python". It also includes a link to the "Using Python on Windows" documentation. Hopefully this will encourage more users to learn about and use the py launcher.

[1] https://docs.python.org/3/using/windows.html#launcher