Because it's paid by taxes, everyone has access and since it is taxes it is % of income. No income means access to healthcare but there's no cost associated to it. A median wage essentially pays their own health care, a high wage subsidizes lower income.

As someone living in a country with this what this means in the end is that I have never in my life considered health care as an issue. I.e. having a job living at my parents house, moving away and studying and so on.

Consider the case of my Mother-in-law. She has enough funds to retire, except that she can't afford insurance plans on the open market, (where they are generally more expensive and less effective) so she has to wait until full retirement age when she'll be able to get coverage from her former employer and ultimately Medicare.