"E492: Not an editor command: PlugInstall" only when I "sudo vim"

My question is a spinoff from this previous question 6 months ago, so to get more details and see how I've installed Vim Plug have a look here.

Currently I wanted to add this extension.
https://github.com/mattn/emmet-vim

Here's my .vimrc file.

 1 2 syntax on 3 map <F5> :source ~/.vimrc<CR> 4 5 set background=light " set background = set bg 6 7 " colorscheme desert 8 colorscheme elflord 9 " colorscheme slate 10 " colorscheme pablo 11 " colorscheme koehler 12 " colorscheme murphy 13 " colorscheme industry 14 " colorscheme torte 15 " colorscheme default 16 " colorscheme morning 17 " colorscheme ron 18 " 19 set background=dark " Setting up background=dark, makes text lighter 20 " 21 " 22 " 23 set nocompatible " Set compatibility to Vim only 24 set wildmenu " Enable Vim's builtin auto completion engine 25 set ignorecase " By default searching in Vin using / command is case-sensitive. 26 " Use 'set ignorecase' to set searching in Vim case insensitive. 27 " Use 'set smartcase' to make search case insensitive if you type the search pattern using lower case only. 28 " 29 set number " Show line numbers. Opposite is set nonumber. 30 " 31 set shiftwidth=3 " Set tabulator size to 4 32 set tabstop=3 " Set tabulator size to 4 33 set softtabstop=3 " Set tabulator size to 4 34 " 35 set wrap " Automatically wrap text that extends beyond the screen length 36 " 37 set laststatus=2 " Show status bar 38 " 39 set encoding=utf-8 " Force encoding 40 set list " Shows hidden characters 41 set nolist " Hide invisible characters 42 " 43 " 44 " 45 " Call the .vimrc.plug file 46 if filereadable(expand("~/.vimrc.plug")) 47 source /home/michal/.vimrc.plug 48 endif 49 

And here's my .vimrc.plug file:

 1 " Plugins will be downloaded under the specified directory. 2 call plug#begin('~/.vim/plugged') 3 4 " Fugitive Vim Github Wrapper 5 Plug 'tpope/vim-fugitive' 6 " Emmet Vim 7 Plug 'mattn/emmet-vim' 8 9 call plug#end() 

Both of these files are located in my user directory /home/michal/, like so:

michal@ubuntu:~$ ls -lah /home/michal/.vim* -rw------- 1 michal michal 20K Jun 21 23:23 /home/michal/.viminfo -rw-rw-r-- 1 michal michal 1.7K Jun 21 23:12 /home/michal/.vimrc -rw-rw-r-- 1 michal michal 203 Jun 21 23:09 /home/michal/.vimrc.plug -rw-rw-r-- 1 michal michal 110 Dec 14 2022 /home/michal/.vimrc.plug.bak -rw-r--r-- 1 root root 12K Jun 21 23:53 /home/michal/.vimrc.plug.swp 

When I execute the command :PlugInstall while I run Vim as michal user, everything works fine.

But when I open Vim using sudo vim and then try to run :PlugInstall, I get E492: Not an editor command: PlugInstall error.

Why is that?

I'm using Vim 95/100 times using sudo vim filename, therefore I need all those plugins I install with Vim Plug, to work in sudo mode.