Why do most people not study Paul's final letters like Ephesians and Philippians?
Most people do not study Paul's final letters such as Ephesians and Philippians because those writings contain the deep doctrines, described as deep water and a higher plane. They represent the deeper revelations given to Paul, and many people simply do not touch them, though God wants believers to learn and grow there.
Les explains that Paul's letters show a progressive revelation. Paul did not cover all the deep doctrines of Romans in Thessalonians, and the further you come into Paul's revelations, the deeper it gets. Finally, you reach the final letters, like Ephesians and Philippians, which Les calls the deep stuff, deep water, a higher plane. Most people don't even touch that anymore because it is deep. This is where God wants us to be; He wants us to learn and grow.