On top of that there are not many funded humanities graduate programs, unlike those in the sciences and engineering.
In practice, graduate degrees were already becoming nearly universal.
I don't think most graduate degrees in law are a good financial investment these days. For some, it works out, but there is a tremendous oversupply of lawyers.
There's also still an overhang of those who graduated during the recession and weren't able to land full-time entry-level legal jobs, a kind of "lost generation" who still aren't in great demand, apparently because employers prefer to take a chance on newly minted JDs over those who never found work in the field, which they fear might signal some kind of problem.