Why companies use thousands of open source tools?

Let's see. We have for instance PostCSS. Yeah, nice idea. You install a lot... and I mean A LOT of plugins. You fill your disks with code and more code... just to avoid writing 3 extra lines of code? I give you and example:

You have this:

.container {
  display: flex;
}

And you have to install a tool and a bunch of lines of code to get this:

.container {
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
}

Really? Are you FUCKING kidding me?

And the worst part of all: Companies are using this SHIT just because Google and Facebook are using it... Sad. Very sad.

Hey, kids from PostCSS. you are great coders. Sure... but if you want to get famous and get seen by the big shot companies, try not to do this. I don't know, do something else, besides creating unnecesary tools, please. We already have millions!