If you are uninsured all your life and accumulate an array of health care needs and you turn age 65, you can enroll in Medicare and have all those needs taken care of no questions asked, no limits and you pay the same premium I do.
And who pays for the accumulated costs your incur? Taxpayers and other Medicare beneficiaries. They pay more because you were successful at the adverse selection game.
So why is it any different for all other Americans? Somebody has to pay.
But of course one should ask why there are any uninsured Americans with a pre-existing condition.