The main reason is that Devuan is at least stable, and it's less stupid than Debian itself (though actually, systemd has the advantage that all the tutorials out there assume that you're using it, which is good for beginners that don't even know what an init is). You can even read reviews, you don't see any complaints about the entire system imploding for no reason, or being slow as hell because of everything being a snappak. You see a lot of those for pretty much every "beginner" distribution, and comments about how the distribution isn't what it used to be.

I don't know what's so hard about making a distribution for beginners, but no one can pull it off. Really, all you need is XFCE (if it's the most stable) and a GUI for the package manager and that's enough. Synaptic does the job, but I guess beginners would like something with pictures so they don't have to look programs up online just to see them. But yeah, that is the only thing that has to be made. How do they manage to screw everything else up?

All that a beginner needs is a tool for installing programs with (just by being an interface for the package manager, not being its own package manager, apparently Manjaro did that, they went out of their way to work extra hard to make things not work), and a system that doesn't break, and maybe configuring the desktop environment a bit. Somehow even that is too difficult.