Earlier quoted context omitted.
For personal use, here's the same thing again. Say a Linux user wants to play a game. The stable old version of their distro doesn't play well with the libs/drivers needed to play the game. So the user must install a newer, less tested, distro. But the goal was not to be "on the bleeding edge" for its own sake; it's playing the game, and there's no other (easy) way.
This is a flaw in Linux Desktops' choice of application management paradigms, which insists that everything be tightly coupled and managed. It is entirely possible and reasonable to have a stable set of base system libraries everyone can depend on and otherwise applications must bring their own.
Of course, NixOS also has atomic upgrades and rollback, so there's not much risk just running unstable everywhere