If your visa condition doesn't ask for it, you don't have to.
Now the reason you want to get one is mainly to avoid MLS. Also, if you need an elective surgery and you are not happy to wait through public system (as it can take a long time for certain surgeries) or if you have to call an ambulance, yes you need one. At the end of the day, for most people, its a matter of peace of mind when it comes to buying or not buying an insurance.