That step (to download the viewer) is non-obvious.
I see no reason why we couldn't have included it in the "Install Windows Features" part of Windows with an automatic prompt upon attempting to open a *.hlp file. The get-out clause "However, the Windows Help program has not had a major update for many releases and no longer meets Microsoft's standards." is very weak considering the perceived quality of actual shipping Windows components. The fact the Start Screen shipped in Windows 8 without an alternative Start Menu cost the company far, far more (billions?) than any potential security vuln in WinHlp32.exe could have.