But without that though, some users prefer old versions over new versions. This way, they can only install older versions such as macOS Sierra and High Sierra. And users with old version Macs need a newer and expensive Mac that most don’t have and also can’t afford. Older models of Mac can’t install the new versions of macOS. You are correct but as the new versions of macOS are coming out Apple is decreasing the list of supported Macs.
You might think why users want to install macOS Sierra when they can install macOS High Sierra, macOS Mojave, macOS Catalina, and the upcoming versions of macOS. For installing this, you need its DMG file. This update was from the unexpected list because before it was the first version of the operating system issued under June 2016.
The macOS Sierra is a pretty surprising software of Apple.