Why did the Messenger, may God’s prayers and peace be upon him, not inform his Companions to send him gifts on any day, and not only on 'Aishah’s day, even though his wives requested that, is this not a matter of justice?

The Companions, may Allah be pleased with them, used to time their gifts for 'A'ishah's day. This was not at the request of the Prophet, peace and blessings be upon him, but rather an action taken by the Companions themselves, and it does not detract from his justice among his wives.

Indeed, the Prophet, peace and blessings be upon him, was just among his wives in his actions. Among these was that he would not travel with one of the Mothers of the Believers except by drawing lots.

He, peace and blessings be upon him, said to Umm Salamah when she mentioned this to him: "(O Umm Salamah, do not trouble me concerning 'A'ishah, for by Allah, the revelation has not come to me while I was in the blanket of any of you women other than her)."

This indicates that it was a divine matter over which he had no control.