That ultimately means that they're locked into what their insurance company mandated health regimen should be. But at least they can sort of choose their insurer, or no insurer (which is usually 10-100 times cheaper on the total medical bill).
All of a sudden, my choice to say, engage in martial arts or boxing, goes from a personal decision (Do I want to do this? Do I have the money for the gear? Is this in my risk comfort zone?) to a decision involving the government (is this behavior too risky for the general pool of insured people?)
Healthcare is not free. Healthcare research and technology is in fact, extremely expensive. Somebody is paying - whether that's the individual via an insurance pool or the government through taxpayers. Does the person paying your bill have your same prerogatives in mind?
I've never seen anything about martial arts, or indeed about sports in general. I'm sure it costs more than £0/year to treat the resulting injuries, just not enough more to make it worth worrying about by comparison.