Why did the Pharisees in Jesus' day see no need of anything?
The Pharisees saw no need of anything because they were self-righteous, filled with their own importance and pomp, and trusted in their covenant promises. They believed they could make it on their own, so they rejected the need for a physician or salvation that requires coming as a sinner.
Les teaches that the older brother in the parable is typical of the Pharisees in Israel. They had been under the covenant promises just like the other brother, but they were so self-righteous and so filled with their own importance, pomp, and circumstance that they didn't see need of anything. When they saw the little element of believers embracing Christ as the Messiah, it made them angry. Like Saul of Tarsus, they thought they could stamp them out by putting them to death and prison. That's the mentality of the self-righteous. Jesus Himself said the well person doesn't need a physician, but the sick person does. Paul makes it plain that you cannot be saved, cannot enter salvation, if you think you're going to make it on your own; you must come as a sinner. That's mandatory.