It's probably just one of those "people are going to do it anyway" things. But I'm not sure if it's better to "do it better" and risk spreading the problem, or leave people with older solutions that fail harder.
Supervisor, runit, systemd, even a tmux session are all popular options for how to run a bunch of stuff in a monolithic "app" container.
Did docker+systemd get fixed at some point? I would be surprised to hear that it was popular given the hoops you had to jump through last time I looked at it