There was a technical reason that WP was used by law firms. When submitting briefs to a court, total word count in a brief is extremely important. WordPerfect counts words in footnotes as part of the document, MSWord did not. This led to one case where the lawyers were being considered for sanctions by submitting a document over the word count limit due to using Microsoft Word.

https://caselaw.findlaw.com/us-7th-circuit/1147966.html