The problem is that when many people move overseas they aren't necessarily covered under a medical plan that the local gvovernment might have in place however the company which you work for my also not give you full insurance coverage either. Especially if you're bringing your family abroad with you, you'll definitely want to get some third-party expatriate insurance.
I've been in the situation where I never would buy insurance- Went years without it, travelled to 30 odd countries, never had a problem. And then one trip I got a nasty eye infection and was out for a week. Not only a waste of time, but also a waste of money. Huge hospital bill, and very poor quality care. I'll never do that again! For the extra money a year, I find it works out really well. It's just not worth wasting your time and money on an unforseen illness.
I've also heard horror stories from expatriates who didn't have international health insurance who have broken a bone, or come down with an even more serious illness only to find out their health insurance was sub-par. You definitely don't want that to happen!
Again though, when bringing your family abroad you really don't want to take the risk. Especially with children as you just never know with them! Expatriate health insurance is by far one of the best investments you can make.
Expatriate medical insurance also isn't nearly as expensive as you might think. And would you really want to take a chance with your health, or your family's health?