In Windows 10 Pro Storage Space, why can't I use ReFS with Parity?

According to discussion at Storage Spaces, Parity and ReFS

• ReFS in storage spaces is available only for two-way and three-way mirroring until Windows 10 Anniversary update incl.
  • see Wolfrevo's answer for workaround
• Creators update brought support for ReFS parity storage space
• Fall Creators update removes ReFS entirely from storage spaces
  • the AllowRefsFormatOverNonmirrorVolume workaround no longer works
  • all the ReFS functionality was moved to Windows 10 Pro for Workstations

Format with ReFS is turned off by default in client versions of Windows (8/8.1/10). You can turn it on modifying registry keys:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MiniNT]
"AllowRefsFormatOverNonmirrorVolume"=dword:00000001

and

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem]
"RefsDisableLastAccessUpdate"=dword:00000001

after that you can format any suitable volume with ReFS