It is important that an insurance company remains profitable so that it can continue to service its client’s claims. If an insurance company agreed to cover all pre-existing conditions eventually the premiums would become so expensive very few people would be able to afford them. For example a person develops a heart condition that requires bypass surgery that could cost up to $65,000 so they decide to take insurance to pay for it. Very quickly anybody who developed a medical condition would follow suit. This would severely disadvantage the average policy holder that would have no, or very few, pre-existing conditions.
If however the insurer agrees to insure this person but excludes their pre-existing heart condition it would mean everybody comes in on an equal footing.
Through prudent underwriting, insurers aim to make an underwriting profit by getting more premium in than they pay out in claims and administration costs. A critical element in this equation is to set an appropriate premium at the outset – low enough to be competitive and high enough to make a profit.