Unfortunately, there just isn't anything you or anyone else is going to be able to do to combat people's "selfishness".
It may not be the way we want things to happen, but nobody is going to be able to convince every facet of the population to give up portions (however small) of their livelihoods to "build a stronger community" for exactly the reason you mentioned: nobody can see that they have anything to gain.
But because insurance works best when the risk pools are largest, and irrational behavior among consumers (ie, spending zero in your 20s and free-riding in your 50s) will prevent those pools from being built organically, this seems like a perfectly sensible place for the government to apply regulation.
Oh, I completely agree on the regulation front - health care in this country is broken right now. I'm not in agreement with the current Administration's plans to fix it, but something needs to be done.
I just think that when people start claiming that "selfishness" is the underlying problem with our broken health care system, they're ignoring the pressures that brought on this "moral decline".
It's really no different than the far-right nutjobs who blame the state of our inner cities on the "laziness" of the people living there.
It may not be the way we want things to happen, but nobody is going to be able to convince every facet of the population to give up portions (however small) of their livelihoods to "build a stronger community" for exactly the reason you mentioned: nobody can see that they have anything to gain.