The souls in Purgatory are faithful people, some of whom are still marred by attitudes unworthy of Heaven - hence the need for the purification wrought in each person by the Holy Spirit. No-one can enter Heaven unless full of gratitude, joy and humility. No-one can go in, still thinking, about his health in earthly life, or other matters: "Why should I be treated like this? I deserve better".
Everyone who dies meets Christ, even people of other religions, and even people who have never heard of Him. They will see Him revealed as their God, and as the Saviour Who died for them. Some will fall down in adoration, believing in Him at last, and will be saved, even if they need purification. Others will recognise Him as the enemy of the evil which they continued to love in earthly life, and despise Him, and hurl themselves away from Him, to end in Hell.
A disobedient man will one day learn the truth. Thousands of souls who persist in mortal sin fall into Hell, at death; yet even people guilty of lesser sins must suffer after death, if they are not fully purified and ready for Heaven. For example: Bishops, priests and theologians who have failed to teach the Faith in its fullness or who have led others astray by their support of heretical ideas.
They are close to God, and safe; yet like the Chinese statues hidden from sight, the Holy Souls wait in a dimly-lit place, enduring their purification, as they think about their past lives, and suffer heartache because they were lukewarm in the Faith, or lacked faith in some of the Church's teachings - or prayed only occasionally, or made little effort to resist temptations, or to become really holy.
The life we lead on earth must inevitably lead to either Heaven and Hell (even if to Heaven via Purgatory). Those who love Christ, and persevere in charity and purity in earthly life, will enjoy Eternal life in even greater charity and peace, with Christ. People who seethe with hatred, ambition or resentment, in this life, and persist in their selfish ambitions, will find themselves in Hell with others who are self-centered and lack love for Christ.
Just as an orchestra member steps forward to make music at a concert without any further practice, after years of training, so those souls whose sins have all been forgiven, and who have done penance, or have gained a Plenary indulgence, have no need for 'training' in Purgatory, before they join the great chorus of praise of God in Heaven, with all the Saints.