I would say the primary purpose of the imaginary time model is to describe observations in a mathematically consistent and useful way. No one is accounting for the ultimate cause of existence, but if spacetime does not require a singularity, then it does not require a singularity.
What should have been the object of the model is a rebuttal to the loss of information in singularities. This has been a big problem all along for those trying to account for the origin of the incredibly convenient physical laws and physical constants. In the lecture, Hawking goes far afield of this goal and addresses directly the belief in a Creator.