The disability insurance isn't specifically for the LOC, disability insurance is to help with any costs should you be unable to continue your schooling/career (yes, LOC payments will be one thing your disability insurance will help with but you will also need money to cover things like basic living expenses depending on the disability, person's financial situation, etc.)
I did med school in Ontario so it may vary between provinces, but almost everyone I know got insurance from the OMA, and a few from RBC I believe. Personally with how cheap it is during medical school (especially via the OMA) I would recommend everyone gets it, you never know if you could get hit by a bus going to school one day and have your future changed forever. UofT in fact requires students (or at least used to) to have disability insurance to even be eligible for their financial aid program.