On Twitter, Erin Monaghan suggests that this simply a holdover from the days when the Michie Company printed the Code of Virginia. (Disclaimer: My father-in-law worked for Michie.) They may have done it in this manner, for lack of any competition or demand for improvement, and now Lexis would rather leave it as-is than face complaints from attorneys that a thing is different than it was and, therefore, bad. As both an origin story and as reason for not improving it, this is better than anything I can manage to think of.