I'm trying to use Node modules (in this example, fs) in my renderer processes, like this:

// main_window.js
const fs = require('fs')

function action() {
    console.log(fs)
}

^{Note: The action function gets called when I press a button in my main_window.}

But this gives an error:

Uncaught ReferenceError: require is not defined
    at main_window.js:1

I can solve this issue, as suggested by this accepted answer, by adding these lines to my main.js when initializing the main_window:

// main.js
main_window = new BrowserWindow({
    width: 650,
    height: 550,
    webPreferences: {
        nodeIntegration: true
    }
})

But, according to the docs, this isn't the best thing to do, and I should instead, create a preload.js file and load these Node modules there and then use it in all of my renderer processes. Like this:

main.js:

main_window = new BrowserWindow({
    width: 650,
    height: 550,
    webPreferences: {
        preload: path.join(app.getAppPath(), 'preload.js')
    }
})

preload.js:

const fs = require('fs')

window.test = function() {
    console.log(fs)
}

main_window.js:

function action() {
    window.test()
}

And it works!

Now my question is, isn't it counter-intuitive that I should write most of the code of my renderer processes in preload.js (Because only in preload.js I have access to Node modules) and then merely call the functions in each renderer.js file (for example here, main_window.js)? What am I not understanding here?