It is just to practice "lấy", and I have heard "lấy chồng" (take a husband) before when people ask me if I've married yet. The point isn't to get the most common phrase, it's to practice specific vocabulary and all the ways you can use that word. It's practicing through context
When translating this sentence to English, why is the response "The man takes a woman" incorrect? As I understand it "lấy" literally translates as "take". Furthermore, when someone says in English "A man takes a wife", it does refer to marriage. I guess the translation "The man marries the woman." is the more accurate, but it is confusing as either English translation is correct in intent.