O Ben Finiti

I am fully convinced of the necessity of prayer (after all, everyone prays), and of the benefit I receive from praying. My prayers change me, internally, in my soul.  St. Thomas Aquinas calls it spiritual refreshment of the mind, and I can truly feel it.

But does it do anything else?  Does it actually benefit or help those I pray for?  If so, why?

Note: I do not ask how; if God wants to grant my prayers, it is certainly within His power.

But why?  Do I have some special “pull” with God?  If I ask Him to heal my sick brother*, will He do it because I asked?  Why not heal all who are sick?  Does He then withhold healing from those who have no brother to pray for them? That doesn’t sound like Him.