Why doesn't Paul call church-age believers sheep and Christ the shepherd?
Church-age believers are not described as sheep under a shepherd because their union with Christ is far greater: each believer is an intrinsic member of the body of Christ, connected to the Head, not merely a sheep under a shepherd. This body relationship secures their position in Christ and a higher plane of Christian experience.
Les explains that Paul never uses the illustration of church-age believers as sheep and Christ as shepherd. Instead, all believers are baptized into one body, the body of Christ, which is likened to the human body. Every believer is connected to the Head, making each one an intrinsic member of His body. This is much greater than being a sheep out under a shepherd. Believers are part and parcel of the Head and the body, which gives them their position in Christ and a higher plane of Christian experience, especially in Ephesians, Philippians, and Colossians.