for me personally, i am not a huge fan of being "over insured". everyone's definition of that term will vary.
most people who travel have medical coverage with their credit card. we were able to get the insurance provider to send us an email that stated in writing that diving accidents were covered. this is what i would do if i were you. but i'm not you.
as someone mentioned above, you must be diving within your training limits. great advice.
i personally (not that it doesnt happen all the time, i'm sure) dont know anyone who has ever gotten specific dive insurance to do their basic ow course. i actually cannot even remember ever being told that any shop i have ever dealt with, provides DAN or any other insurance to students. so i find that whole thing very interesting.
our shop had insurance for the staff etc of course, but in the ten years i worked there, no one ever even mentioned anything about insurance for students. hmmmmm.
all insurance is a numbers game. are you willing to assume the monetary risk in order to save the cost. period. so it is always up to the individual to weigh the risks vs costs and decide whether they feel it is worth it or not.
as a new student doing a small number of shallow easy training dives, the risks are very very low that anything will happen. but if the cost is so cheap that you feel better about having it, then perhaps you should.
if you were an advanced deep diver that dives 1000 dives a year in remote locations etc etc, obviously the risks are exponentially higher that something bad might happen. so perhaps in those cases, no matter the cost, the insurance might be considered mandatory.
perhaps consider using a shop that does provide the insurance you want? if there is one avail.