Community rating is where an insurer would be prohibited from charging policy holders different prices on the basis of risk. It is viewed as an essential part of health care reform by progressives and even some conservatives. The motivation behind community rating is sensible, some people have conditions which they have no control over and when insurers consider said condition the price of a policy is likely to be unaffordable. This is unfortunately what insurers do. Some view this as sinister but it too is sensible.
An event that is likely to occur is not an insurable event. If I wanted to build a house in area where hurricanes hit annually and houses were frequently destroyed the only way for an insurer to make a profit (or stay solvent) would be to set my premiums at the level of an expected future payout. Otherwise, given the predictability of a payout, a premium any cheaper would essentially constitute a direct transfer of wealth from the insurer to me. However, the information conveyed by the premium price is valuable. It tells the prospective homeowner that unless the homeowner is able to build a house that can withstand repeated hurricanes (or frequently rebuild a house that can't) that building the house is probably not advisable or affordable.
If you allowed insurers to price their premiums on risks where the policy holder has control over, such as their weight, activities such as smoking or excessive consumption of alcohol, or indicators such as high cholesterol or high blood sugar you would provide policy holders with stronger incentives for healthier lifestyles. This is not to say that all policyholders would adjust their behavior but at the margins some would. This would not obviate the need for other insurance reforms such as guaranteed issue and renewal, prohibition on excluding policy holders with pre-existing conditions, catastrophic re-insurance, and ex-post readjustment. But it would lead to a healthier population and lower health care costs over the long term.