Not a lawyer, but once you've acquired that knowledge, you have it forever. It's not like LaTeX changes very often (unlike, for example, Microsoft Word)
LaTeX is great for typesetting documents; easy to work with autonumbering, even nested and subnested lists. There's even a Koma-script package for legal documents (jura). But Word does a better job of redlining. And it is the standard, though there are a few offices that still use Wordperfect for the "Reveal Codes" feature. If your output is paper or a paper substitute like pdf, you can use any word processor. But if you need to collaborate, you need a 100% compatible Word processor. On Linux, it's Softmaker Gmbh's Textmaker. 100% compatible and a lot cheaper than Word. Odd that no one has mentioned it.
Microsoft Word is also quite stable, certainly in terms of functionality and especially backwards compatibility. They know how much money they make just from the immense inertia of being in the lead for 30+ years, and they don't kill off that golden goose.