I think normal users do have a fear of installing software on desktop. There's this fear of "viruses." They know they exist, they don't know how they work, but they know you shouldn't install anything or you'll let them in. They view third-party software like vampires - intruders trying to trick them into opening the door.

Which, given the history of adware toolbars and registry bloat on Windows, is maybe warranted.

https://www.pcworld.com/article/149951/registry-cleaner.html