https://www.digicert.com/blog/https-only-features-in-browser...
A static page that hosts documentation on an internal network does not need encryption.
The added overhead of certificate maintenance (and investigating when it does and will break) is simply not worth the added cost.
Of course the workaround most shops do nowadays is just hide the HTTP servers behind a load balancer doing SSL termination with a wildcard cert. An added layer of complexity (and now single point of failure) just to appease the WebPKI crybabies.
Just about every web server these days supports ACME -- some natively, some via scripts, and you can set up your own internal CA using something like step-ca that speaks ACME if you don't want your certs going out to the transparency log.
The last few companies I've worked at had no http behind the scenes -- everything, including service-to-service communications was handled via https. It's a hard requirement for just about everything financial, healthcare, and sensitive these days.
[proceeds to describe a bunch of new infrastructure and automation you need to setup and monitor]
So when ACME breaks - which it will, because it's not foolproof - the server securely hosting the cafeteria menus is now inaccessible, instead of being susceptible to interception or modification in transit. Because the guy that has owned your core switches is most concerned that everyone will be eating taco salad every day.
Of course, then there are the employees who could just intercept HTTP requests, and modify them to include a payload to root an employee's machine. There is so much software out there that can destroy trust in a network, and it's literally download and install, then point and click with no knowledge. Seems like there is a market for simple and cheap solutions for internal networks, for small business. I could see myself making quite a bit off it, which I did in the mid-2000's, but I can't stand doing sales any more in my life, and dealing with support is a whole issue on it's own even with an automated solution.
Someone that has seized control of your core network such that they were capable of modifying traffic, is not going to waste precious time or access modifying the flags of ls on your man page server. They will focus on more valuable things.
Just because something is possible in theory doesn't make it likely or worth the time invested.
You can put 8 locks on the door to your house but most people suffice with just one.
Someone could remove a piece of mail from your unlocked rural mailbox, modify it and put it back. Do you trust the mail carrier as much as the security of your internal network?
But it's not really a concern worth investing resources into for most.
Ah, the "both me and my attackers agree on what's important" fallacy.
What if they modify the man page response to include drive-by malware?