Sure, the 'rainy day' scenario was brought up a couple of times (by my Mom). I reassured her; a portion of every paycheque was going into my savings account, but even still, there was nothing to worry about. In March 2010, I calmed my mother's fears for not opting into benefits by telling her I was "young and healthy".
Fate swiftly intervened.
In March 2011, when my contract was renewed again, I did not think twice. After barely surviving a 15-week sick leave on the government's measly paycheques, and forcing myself to go back to work before my treatment was over, I knew better. Not only do my benefits cover my teeth cleaning, monthly medications (planned and unplanned), sick days and vacation, but they give me the piece of mind I lacked during treatment. No amount of money added to your paycheque or in your savings account can reassure you that you'll be ok when shit hits the fan. That's what insurance is for.
Now, I pick up my medications even if I have $6 in my bank account, and I take a sick day when I'm not feeling 100%. And even though I just barely made it through my treatments without totally breaking the bank (though I worried about needing the uncovered, highly expensive drug called Neupagen everytime I went in for a blood test), I don't recommend it to anyone.
No matter how old, young, healthy, or at-risk you are, you will regret not planning for that rainy day. Get health insurance.