Obviously we can't know why, though there are several factors which have been mentioned above, chief amongst them Crowley's ambivalence to The Book of the Law at the time. Nor was this an isolated occurrence of a return to Egypt being suggested. By Crowley's account, the Abuldiz Working terminated with an instruction for Crowley to go to the desert in search of an egg under a palm tree; unfortunately, the record of the Abuldiz Working is incomplete. However, the theme was picked up in the Amalantrah Working of 1918, Crowley being exhorted to go to Egypt. I recall reading Crowley saying somewhere or other that Amalantrah and Abuldiz contacted him in order to get him back on track; as such they can be regarded as masks of Aiwass.
In spite of successes, Crowley didn't really trust the Abuldiz and Amalantrah Workings, and the same goes for the Shanghai Working of 1906 with Elaine Simpson. In the record of the Amalantrah Working there are records where he is waxing very enthusiastically about the accuracy of everything Amalantrah is communicating, only to be followed by another session where he is very cynical about the worth of anything Amalantrah had to communicate, even going so far as to disrupt the session in his frustration..
He never did go back to Egypt. Gerald Yorke did say in correspondence with Jones in 1948 that Crowley did make plans to go to Egypt, but that these plans never came off.
Thus the only conclusion we can draw from all this is that, despite the reception of The Book of the Law being the major event of his life and work, for some reason or another he had an aversion to going back to the scene of the revelation. We can't, I'm afraid, know the reasons for this reluctance.