In speaking to them, Matthew is addressing our needs and concerns as well. "No one knows when; so, stay ready."
Jewish hope and Christian hope had (can I say "has"?) been for a Messiah to come to rescue them from their earthly enemies and troubles by setting things right. No more war. No more poverty. No more oppression. No more sin.
If we think that the Messiah is coming immediately and will end the world as we know it, we might be tempted just to sit around and wait for that event. But, that attitude might interfere with our living our lives the way God intends.
With the rescue, Matthew ties in judgment. He cites the examples of many who had been living lives not in accordance with the ways of the Lord. He warns, "If they had known when, they would have prepared; so, you be ready."
Someone once told me the difference between prophetic and apocalyptic texts is that prophecy is telling us to change, but apocalypse is saying that it's too late to do anything about it, just hold on, it's almost over. Then someone else later told me that the prophets were also calling for perseverance and the apocalyptics were also calling for repentance. Whoever is right about that, I am hearing both repentance and perseverance in Matthew's text. And, I think both attitudes are appropriate for us to assume in Advent.