They probably also thought ahead a bit on how it would wind up getting abbreviated, used, or misused by the public. I recall when the XBox One came out and everybody called it the XBone, several folks on the XBox One team were upset about it.

If there's a Windows 9 it might eventually turn into Roman numerals, so then you've got Windows IX, which could turn into Winix or Wix, or in a particularly bad case "Windows Icks".