The 7zip self extractor is a false positive for the advanced threat defense (behavior defense) of many antivirus products. Therefore it make sense to use another system. Here i provide a free installer system which is not a false positive and maybe also easier to use than the 7zip self extractor.
http://nsis.sourceforge.net/Main_Page
http://www.chip.de/downloads/NSIS_17011992.html (german, but show the good reputation)
https://en.wikipedia.org/wiki/Nullsoft_Scriptable_Install_System

Does NSIS not cause a false positive because it is safer, or because it is less widely used?

I think good and easy one