I work in this niche. I actually work a niche within this niche, and have implemented solutions. We do have a couple competitors. But most new players in this arena come in with exactly that statement - "oh, this is like programming, lets bring in markdown and git and solve all the things!" Then they realize that the level of detail and the expectations of legal document authors are far higher than they ever expected. Markdown doesn't cut it. HTML doesn't cut it. CKEditor and tinyMCE don't cut it. We spend a huge amount of effort re-writing plugins for those editors to meet the actual expectations, and defining new data formats for all the citations and interlinking of legal documents.

Not that there isn't room for competition - there is. But the barriers are not what people expect. And the easy answers that coders tend to see aren't the real problems.