Parables are a 2nd tier teaching of Jesus. The 1st tier is a direct proclamation that the Kingdom of God is near and forgiveness of sin is available. Some don't hear/understand this 1st tier, hence Jesus goes to the 2nd tier teaching method, using parables.

One son, after being asked to work in the vineyard says, "I will not." The second son, after being asked to work says, "I will, but didn't go." Which did the will of His father? In the second parable, a vineyard is lease to tenants. When it came time to collect the rent, the servants of the vineyard owner were beaten and killed. This parable is also explained.

A rich young man comes to Jesus asking "what must I do to inherit eternal life." This dialogue provides the context for understanding the parable of Labors in the Vineyard.