Catholics remember the faithful who lived outstanding lives before them. More so the ones who had dedicated their lives to others, living not for themselves but for Christ; for humanity.
They remind some of us that although we have challenges in our own lives, it's possible that we can be holy, we will overcome. The Catholic Church is the church of the apostles. These people become our role models in the Christian journey. That's why majority of Christians first names are derived from names of early Christians who are perceived to have led exceptional lives.
Most Christians believe that when good people die, they go to heaven from where they inspire us and watch over us. Catholics believe these people pray for us.
As to who is supposed to benefit from these rites, the answer is; to the living.
Sister Irene beatification ceremony shows that good deeds never die and she inspires a generation to dedicate their lives to Christ. She shows that no matter who we are, wherever we are we can make a difference and make the world a better place to be.
Democracy does not belong to the dead