I think health insurance is for everyone, because the risk of having expensive health problems exists for just about everyone, especially if health issues due to accidents are included. This is similar to automobile insurance - everyone who drives carries insurance, not just the bad drivers. However, insurance companies of all types love to have reasons to divide people up into very small risk pools, and charge people more for insurance if they have even a casual relationship to some risk factor that indicates that they may make claims (or higher than average claims) against insurance. In the US, auto insurance companies are using things like people's credit score to determine how much to charge them for automobile insurance, on the basis of a belief that people with certain ranges of credit scores are more likely to be involved in accidents, apparently.
For health insurance, the risk of the health companies getting access to too much data about individuals is that they will start charging individuals for insurance according to their perception of the risk of insuring those individuals. Even if they could correctly screen people into various risk categories, this would be detrimental to the overall way insurance works in general - a large pool of people are charged for insurance based on the average risk in the pool. Everyone pays a more or less affordable rate, and when the risks materialize as claims, those claims get paid off, but the insurance company doesn't have to pay out more than they took in (if they did, they would go out of business).
If only sick/unhealthy people get health insurance, then the cost of that insurance has to be high, because they will have a higher rate of claims. Those who are fortunate enough to have great health might forego insurance, but on average most people expect to have some issue or other that might require insurance coverage, so on average most people will want insurance. So more people get insurance, and the average cost of insurance goes down because the average claims rate across the larger pool is lower.
The higher the certainty of people making claims, the less of a solution "insurance" is - insurance is intended to spread risk among a large pool. It seems to be very hard to get people to understand that on average, people cannot expect to get more out of an insurance plan than what they pay into the plan. If that were so, the insurance company would go out of business. As much as people may dislike insurance companies (and many insurance companies have earned the dislike/hatred of their customers), they provide a substantial social benefit when they perform their basic risk management function.