One commonality between the spaces that exist in the back rooms are ones that emulate doctors offices, malls, corridors, pools, playgrounds, etc. all of these are either public or pseudo public spaces (like big box stores). Also there is a nostalgic quality to them, they all exist in a “built in the past” sort of context.
I think they’re more a fear of “waiting” sort of spaces. Spaces that don’t serve any useful purpose but to waste your time as you travel through them. I think it stems from the fact that so many of us have so little free time in our lives, that simply travelling from place to place (and wasting time doing it) is subconsciously terrifying. In particular, traveling to and from work is an awful part of most people’s day, but it is so normalised that people can’t even comprehend that it is upsetting and unpleasant. So people project that frustration of capital both demanding every second of people’s time, but also not using that time in a productive way.
But then the kids got their grimy hands all over it and now it is basically just RoNiteCraft: the wiki, and is just a collection of vaguely video gameish “lore” about random monsters and their power levels and bullshit like that.