They could have had file permissions. They could have had a package manager instead of third-party installers.
Also note that Microsoft Office has a long history of not following Windows rules. Microsoft didn't even set a good example.
In the era of Windows 95, having a network connection was still a rarity. Expecting modern systems to have package management and sandboxing mechanisms would have been 20 years ahead of their time.
In the era of Windows 95, having a network connection was still a rarity. Expecting modern systems to have package management and sandboxing mechanisms would have been 20 years ahead of their time.