One practical advantage of using free tools is that everyone in your company can use it, you can write automation that uses it, etc. I'm not going to defend LaTeX in particular, but there's a lot of value into using something (like Markdown or reStructuredText or whatever) that anyone in your company can propose edits to, where you can automatically publish nicely-formatted (e.g. HTML) documentation when anyone in your company makes a change, and so forth.

Another way of gaining this advantage is to use something you're already paying for like an internal wiki.