[devnullbrain]

>If the only installer available was one provided by the OS

There's the non-sequitur. OP never said that this is what should happen. It is strange to leap to this assumption while also wanting to define portable programs and archives as 'installers'.

In the context of Windows, 'special' installers means the programs you run to be able to use a different program that don't appear on other OSes.

[daemin]

I did not define portable programs and archive extractors as installers, just suggested the act of decompressing to a directory or copying to a directory would be considered as installing the program.