The Church can grant a plenary indulgence to anyone who seeks it, but she cannot retroactively apply it to someone who is dead. It requires the active cooperation of the one who seeks it, not a passive acceptance. In other words, the Church has a storehouse of spiritual treasures, based most heavily on Christās sacrifice, which also contains other peopleās sacrifices, almsgiving, and so forth, their corporeal and spiritual acts of mercy. She can apply it to those seeking to amend their lives and who cooperate with Godās Will.
If the Church just flat-out granted them to anyone she sees fit or anyone who says he wants one but doesnāt want to do whatās required to gain one, she is denying the role of free will in our salvation. She would then in essence become like a overindulgent parent, letting children get something for nothing. That is the Lutheresque model; sit back, stay sinful, and let God do all the work. Yes, He gets the credit, but thereās a whole lot of Scripture that contradicts such quietism.
Since Christ requires us to drink the cup He drank and be baptized in the baptism He underwent, He expects us to take up our crosses and follow Him. We are called upon to suffer and make sacrifices, for our own spiritual good and the good of others around us.
In other words, we donāt get the bonus without the onus. Even a plenary indulgence (which is incredibly difficult to get, by the way) requires our cooperation, free will actions and some sort of sacrifice, and even then, itās not a guaranteed ticket to Heaven. We can toss it away if we commit another mortal or even venial sin. It isnāt permanent.