Simply this - God, as a host, is not only lavish, but demanding. His table is not only a masterpiece of culinary art and domestic elegance, but a school for etiquette. If we come to God's banquet, we are expected to behave ourselves. Apparently, many don't believe it is. Although today's Gospel historically refers to official Judaism's rejection of Christ and His message, and the subsequent destruction of Jerusalem by the Romans, the message doesn't stop there.
Christians are really the guilty ones.
We proclaim that we accept the invitation to Christ's banquet, only to poison our response with a long list of variables. We don't want heaven as it is, but how we would like it to be. We're worse than those guests who refuse to come to the banquet. At least they had the courtesy to offer their host a excuse. We come, thinking were doing God a favor, that somehow our rude presence just can't be missed.