As only pure devotees are promoted to the spiritual world, why are doorkeepers needed there?

In the Bhagavatam, it is described how only pure devotees are   promoted to the Kingdom of God (verse 25). What is Jaya and Vijaya’s   job description? The duty of a doorkeeper in the material world is to regulate entry of people, but anyone who has reached Vaikuntha should not be denied entry (verse 32). As it happened, they denied entry to unfamiliar persons and got punished.