I'm pretty sure in Australia it is because it is actually much cheaper to teach law than medicine.
The commonwealth funded student HECS rate is the same for both degrees, but that is because it is assumed that lawyers will earn a lot. Conversely vets get paid poorly in Australia, but the HECS fees are in the top band because the course is so pricey to teach.
I don't know where an Australian law degree qualifies you to work but my UNSW trained uncle had a successful career in the Cayman Islands and I know friends who are off to London etc. I guess law is the kind of thing which is always going to require country specific re-training though.....