If you have the $50,000 to $100,000 that an evacuation and chamber ride might cost, and spending it wouldn't be a financial disaster, then save the $100 on DAN.
Of course the fact of the matter is, that if you have $50-$100K to toss around without a significant financial impact, you're probably a pretty smart cookie. Smart enough in fact to realize that the $70 for DAN master insurance is money well spent. (ie: few people get rich by being foolish)
If your medical insurance covers it (and I don't see why it wouldn't), save the $100.
The fact that you "don't see why they wouldn't cover it" doesn't change the fact that medical insurance won't typically cover evac, chamber, etc. They certainly won't cover hotel, transport, lost gear, lost dive days, etc as result of an accident. Nor will they typically cover ANYTHING if you're in some remote 3rd world dive location, where DAN usually will.
I'll stand by my earlier statement. Anyone who dives without dive insurance is a fool.