Yes, that is what I mean by my last point: "It allows for portable installations and to run software just copied from other sources." You can think of decompressing from an archive as running a very simple installation program.

If the only installer available was one provided by the OS how long do you think it would take to make that the only way to install and run software. These things are being done right now on many platforms in the name of safety, security, and to a lesser extent convenience.

The more phone-like a platform is the fewer ways you have to install and run software on it. So far general purpose computers still allow you to install software in other ways than the built-in method (i.e. just unzip and place in a directory), but it's getting increasingly common to require executables be signed, and things are always moving to be more and more locked down.

Now the use of "Special" installers/uninstallers is from the original comment, I would just refer to them as "regular" installers/uninstallers. I do like the ability and freedom to have an ecosystem of these things, as I don't want the one OS method to be the only way to install applications.