If we are still single by 29 then we will marry each other?

One of my guy friend made this pact with one of my friend(they are both 20 and single)...why do people do that????.Is he attracted to her or somethng....because she said to him Oh i think i am gonna stay single forever and then he said no you wont be because if we are not married by 29 then i will marry you.....I would love them to date each other...soo just wonderng if he is attracted to her or what???