What is the point of marriage? What does a healthy marriage look like? What is human love?

I probably sound like I'm from another planet phrasing it that way...I just can't wrap my head around what the point of marriage is and what a healthy marriage looks like to what human love is. I don't believe marriage is practical, as people change throughout their lifetime and sometimes naturally drift apart even when both do their best...and as for love, at the spiritual level I believe in unconditional love spiritually from the Divine Power but I don't believe humans are capable of consistently showing and embodying unconditional love. I believe we as people are only capable of conditional love when we look deep within ourselves and one another. I'd like to believe otherwise but I haven't seen proof of it...