[ad]It’s a bitch trying to hitch a wild horse, so it’s reasonable to assume that one must appeal to the upper half of the centaur if you want to marry him. The higher mind of a Sag studies the religious or philosophical foundations of marriage. The animal self wants to just gallop off to distant lands and impregnate many mares.
Therefore, a Sagittarian’s faith, his religious commitment, would be a primary motivation to tie the knot. If God says a man and a woman shall unite and make babies, then Sag will be the first one to jump onto the bandwagon. He’s not a conformist, but he’ll do what everyone else is doing if there’s an inspiring reason to do so.
Not all Sagittarians are God-fearing folk, though. This sign relates to both the legal system and foreign lands, so obtaining a green card would also make him want to exchange rings. If he’s truly in love but bristles at the idea of being constrained by a piece of paper, he’ll do it anyway to keep his beloved in his country. Or if he’s not really in love but his student Visa ran out, he’ll exchange vows just so he can stay overseas.
Comment below: Are there any other reasons for a Sagittarius to get married?