I think it is cultural. It's kinda like building your own lightsaber as a Jedi. The part of Emacs/Vim initiation is building your own configuration that works for you. Setting up plugins, keybindings, colorschemes etc. It's part of the fun of it (at least for me).
Oh yes. What other software allows you so much to make it your own? Yes, I know the yak shaving argument etc. But what's the fun in opening up some computer/OS/software that looks and feels exactly like everyone elses? An Emacs (and vim) setup is something you can actually have a discussion about with someone else.
KDE, various window managers (i3, awesome, xmonad,...), the Linux kernel (there's so much stuff you can configure through sysctl alone, and that's just 1 single customization facility), SystemD, your shell (whether it be bash, zsh, csh, ksh, or something else), and the list goes on.
And then slowly over 20 or so years deleting all of it.
I think I'm down to about 110 lines of ~/.vimrc now :}