Here is the simple answer:
A 'true' or 'legal' marriage NEEDS always a 'third' party (or person) that is representing the law of a Community or a System in order to confirm it or, in the least, blessing it.
In general (since there are always exceptions), without this 'formal' procedure, a man and a woman cannot live very close openly (as married couples do) while expecting being fully respected by the families living in their neighbourhood and by their colleagues at work.
And this is not the end of the story
Also when a man accepts a third party to bless his marriage, he also accepts and confirm freely to be a follower/believer of the side that blessed his marriage. Otherwise his marriage would be not real.
For example, if a Christian gets married by a non-Christian law, he is seen automatically as a sinner living with a strange woman. But at the same time, he and his wife are fully accepted by the community (or System) that blessed (confirmed) his marriage.
As you see, a real marriage and real friendship are exclusive.
A true friendship unifies two free independent mature persons, spiritually speaking, without the need for any other one in the world to give them any sort of permission about their friendship; no matter how long it may last. Am I wrong?
In the contrary, a true marriage unifies two complementary living fleshes under a certain regulation/law after being approved by a third party, in a way or another.
Corollary:
Every sect of any religion and every formal system/belief/culture in the world SHOULD have its own law about marriage, otherwise it won't exist for too long.
Now, could you imagine Jesus asking a man (or a woman, if you like) to bless his marriage with a woman?
And since I used living the unconditional love towards all others without discrimination, I couldn't see myself following freely ANY specific law of marriage in the world and belonging therefore to its group, community or System. So it was out of question for me to get married (fortunately, I also never felt the need to have sexual relationships with any person
, perhaps because I am just an intellectual and spiritual being
)
Now tell me... didn't you all know already this common prerequisite?