Alone with Prabhupada, I asked about book distribution and Deity worship. I asked why, if Deity worship was the process for self-realization in the last yuga, do we have it now? Wasn't sankirtana sufficient?

He said that he had introduced worship of the Deity because, while there may arise differences of opinion about the distribution of books, on the point of  there was only one standard on which all must agree. This would therefore maintain the purity of the Movement.

(From Hari-sauri Prabhu's Transcendental Diary)