Large companies do this.
Small companies/small groups of developers have no idea how to implement and manage this, but think that it should be easy.
I've recently been approached by a group of developers to enable SSL on their internal sites. When I mentioned that this would take some time, the response was "why can't you just use LetsEncrypt?"
I replied that LE only works on external facing sites, not internal sites. The next response was "fine, why don't we make it all external facing?"
I'm still trying to explain that their CI server (Jenkins, with its history of remotely exploitable vulnerabilities), and their internal OAuth2 server should not be public facing.