Those wouldn't go away without the government recognizing marriage. They would become more complicated and less clear. The entire point of most of those laws and regulations is to make things easier and more efficient so that the courts are not tied up with stuff that is easily taken care of with laws or regulations to cover the vast majority of these issues.
Spouses are part of the hierarchy for legal kinships, and they are at the top. Barring some legal contract to the contrary that was made up after a couple got married, the spouse has legal say of things such as medical decisions and after-life decisions (burial, cremation). For an unmarried person, the person with that legal say is going to be a parent or next down the line in legal kin (sibling, grandparent, aunt/uncle, etc.). This also means that the spouse has a legal responsibility to pay for final expenses.
Splitting up property in the case of a separation for all those people would be a nightmare for the courts because they would have to decide when the relationship was truly established. With marriage, you take the date of marriage. Visitation in many hospitals is limited to legal family only when it is serious, but without marriage, there is no legal kinship, no matter how many contracts or legal documents they have written up between them. And the military uses legal kinship, immediate family to determine who to allow as being claimed a "dependent", which includes being covered by medical and dental insurance, and even a life insurance policy, not to mention an ID card to give base access. By just allowing people to choose whoever they want to be their dependent based on them just saying so, it easily can lead to security issues along with a lot of extra money being spent by the government.
There are so many more things as well.