And users get upset if you force them to switch to LO, because it's not perfect at rendering Word documents (because MS doesn't want it to be).
That simply is not true: Microsoft opened up the file format many years ago. The problem with file fidelity is that to achieve identical rendering, you must FLAWLESSLY mimic every single behavior of the source program, including bugs.
LibreOffice not only doesn’t have all the features and functions of Word (no matter what its proponents claim), but moreover, Word uses a quite unique document object model that nobody else has wanted to copy. Translating between that and the more common tagged format of LibreOffice etc is nontrivial.
The Word object model was invented back when computers had very little RAM. The problem with ordinary tagged formats is that to determine the formatting of any piece of text, you must parse the entire document from the beginning, since it could be affected by an opening tag right at the beginning. To allow users to edit text that can’t fit in memory in its entirety, Word completely divorced formatting from the text itself. Instead, spans of text have no formatting within them, but instead are associated with a stylesheet which contains its entire formatting. If you select a word and bold it, for example, it breaks up the bold word and the spans before and after into different spans, and the bold word gets a different stylesheet. The association of text spans and their styles is kept in a separate table, which also tracks the order of the text. So not only is the text not formatted with tags, it can be physically stored out of order! (The original binary file format is actually basically a lightweight file system.) In the past, when disks were slow, like floppies, Word even defaulted to “fast save”, where it just appended modified text to the end of the file and amended the association table to refer to the new text spans, rather than rewriting the entire file. (Yep, this meant that you could roll back edits, which led to the leaks of sensitive or embarrassing information!)
None of that design is necessary today, but that architecture remains. And nobody else stands a snowball’s chance in hell of reproducing it, since it’d be a mammoth undertaking.