Why is getting married so important?

Depending on how you view creation, we may all be either related or unrelated, or some combination of related and unrelated. I am not sure what you mean by "there is no such thing as love between unrelated people," but regardless of how you view relatedness, there is certainly love for our fellow beings in a platonic sense. There is love in a companionate sense which leads some to marry, and there is love in the perhaps naive and romantic sense which often enough leads people to rather short-lived commitments if the divorce statistics are any indication of how well 'emotion-based' relationships work.

While you are not sure if love exists between unrelated people, I am not sure if such a thing as an "open marriage" exists by definition. By definition, a marriage is a consensual union between one man and one woman. It is a commitment to live as husband and wife for at least, "as long as you both shall live" and in some cases "for all time and eternity". There are only two people in a marriage. Anything else ceases to be a marriage. It is polygamy or polyandry, or promiscuity and multiple partners, or a harem, or what have you. It is not a marriage. Open and marriage are two mutually exclusive terms, also known as an oxymoron. Your reference to drugs and addiction is ironic in that the concept of an open marriage was one result in the United States of the drug-induced confusion and depravity of the 60s and the pornographic addictions of Hugh Hefner's 70s, both of which failed miserably in liberating anyone unless you consider rampant disease, death, divorce, and the fragmentation of the family and to a large extent the souls of millions a form of liberation.

Within Christianity, the proposition is unthinkable. Outside of Christianity, there have been harems, or what the biblical traditions have referred to as whoredoms, which term derived from the root word hora, associated with the goddess hora, the natural order, and fertility worship, usually denoting the allowance for anyone to enter indiscriminately in the process. It is a very non-Christian proposition. I think you would be hard pressed to find any good Christians who wouldn't be horrified much less who would accept it. If I understand the proposition correctly, it is to spin extra people in indeterminate numbers in and out of a two-person dyad, something analogous to shoving people onto and off of a spinning merry-go-round until someone gets tired or sick. Then it's over and on to the next. It is all together hedonistic, based on self-seeking and personal gratification, and is not a foundation for much more than fragmentation.

I take your use of the phrase "marriage is a way to tie myself down" to mean that there is in your view some recognition of a commitment in marriage, even if it is one you would clearly wish to avoid. I agree. Marriage is a commitment. If you do not wish to make one, then you don't marry. But I think I see commitment as less an obligation, more of a duty that is a privilege, and more giving of self than it is tying oneself down. Marriage is about wholeness with one person. It is about sharing wholeness with one person who is your spouse and none else. That's what monogamy is. It is not open to fragments, parts, pieces, and revolving doors. How many people can handle that commitment to just one person, to love that unselfishly, that deeply, that unconditionally, I do not know, but I do know that that kind of love exists. There are many examples of it around us if we care to search for them.

 

You can have everything that marriage offers without "actually" marrying? So, then "actually" marrying involves something more than just getting the same stuff without "actually" marrying? "Actually" marrying involves an actual marriage record, an actual authority that recognizes and supports the marriage, witnesses of some kind. It involves the actual rights, privileges, and status in a given society of any actual children that may potentially become party to the marriage. In a society that requires vital records, tax records, living wills, power of attorney, insurance beneficiaries, there is paperwork involved, and required, typically, for nearly every other indication of status and relationship. That a marriage license and a marriage certificate should be left out of the commitment, I don't quite see as reasoned or realistic. If there are children, there will be birth records with parents names attached to them. There will be education records with household composition listed. There will be tax returns with dependents listed on them. There will be employment records with health insurance beneficiaries indicated. Why opt out of a marriage record that reflects what all the other life records will reflect? If the commitment is in the paper trail elsewhere, why not put it, too, on the record and call it what it is? In our society, practically speaking, the marriage record affords higher status to the parties and their children if there are any. It will take precedence over common law and natural union if ever an authority of the state were invoked, so unless one were 100% certain of never needing to invoke that authority, it would be in the best interest of the marriage and potential family to have it properly made a matter of record.