We are told by the Church many times the importance of prayers for others. It would seem that we can help other people by praying for them, or, to be more precise, we can plead God's grace for those who we pray for.
Let us reverse this statement. Then it would seem that if we don't pray for others, then God will deny them His grace He would give them if we were praying for them.
This seems to be almost explicitly stated in Fatima apparitions:
Pray much and make sacrifices for sinners, for many souls go to hell because there is no one to make sacrifices for them.
Does this mean that God preconditions His aid for sinners on other people's prayers? If so, why? How to reconcile such a statement with God's infinite love, according to which He should do whatever is possible and whatever will not violate a man's freedom to save them from eternal damnation and bring them to Heaven? Since the fact that no one prays for a man is hardly their guilt, how to reconcile such a statement with God's fairness, according to which he probably shouldn't precondition His actions towards a person on anything other than that person's will, and especially not if eternal salvation is at stake?