There is very much a legal point to getting married. In many countries you have few rights in law as an unmarried couple. You might not worry about this, when you are young but as you get older it becomes an issue.
For example in many jurisdictions if your partner has children from a previous relationship, and he or she dies, they can force you to sell your home.
Once your partner dies, his/her family own the body and though you may know the kind of funeral ceremony he/she wants you have no rights at all. The family can even exclude you from the funeral ceremony.
Yes it is a piece of paper, but that paper gives you both security and legal rights. More importantly it safeguards both couple and any children from the relationship.