Why does vw include the scrollbar as part of the viewport?

Question

I'm trying to build a website that has lots of boxes that are of equal width and height. For example, I have a page that has 2 equal size boxes side by side.

The simple solution was to set the width and height to 50vw. This works great until there is a scroll bar. I've Googled around for hours and can't understand why on earth vw and vh would include the scrollbars as part of the viewport.

Here's a sample of my issue

HTML

<div class="container">
    <div class="box red"></div>
    <div class="box green"></div>
</div>
<div class="lotta-content"></div>

CSS

body {
    margin: 0;
    padding: 0;
}

.container {
    width: 100vw;
}

.box {
    float: left;
    width: 50vw;
    height: 50vw;
}

.red {
    background-color: red;
}

.green {
    background-color: green;   
}

.lotta-content {
    height: 10000px;   
}

Notice the unwanted horizontal scrollbar

https://jsfiddle.net/3z887swo/

One possible solution would be to use percentages for the widths, but vw for the height, but it won't ever be a perfect box which isn't the worst thing in the world, but still not ideal. Here's a sample

https://jsfiddle.net/3z887swo/1/

Does anyone know why vw/vh include scrollbars as part of the viewport? Also, if someone has a better solution than my own, I'd love to hear it. I'm looking for a pure CSS solution. I rather not have javascript.

Answer 1

I have a different answer, and feel the need to share my frustration

BECAUSE STANDARD-MAKERS ARE STUPID

(committees, in general, always are)

One simple (simplicistic) workaround is keeping the scrollbar always around and be dealt with it

html,body {margin:0;padding:0}
html{overflow-y:scroll}

(use overflow-x for a layout that uses vh)

I believe they seriously screwed the pooch on this one.