Then why do people in the roman church go to confession every week????
Oh, if only I were as devout as you say! It's been six weeks for me, and if I don't go tomorrow I will feel I've got a terrible back-inventory to account for.
You might more accurately have asked, "Why do really devout, holy Catholics --- for instance, many of the canonized saints --- go to Confession every week????"
I suppose for the same reason I wash my dishes on a fairly regular basis, launder my clothes, and weed my garden: because these things call for constant maintenance.
When I was a know-it-all quasi-Catholic-pagan at age 18, 20, 22 (i.e. back in the Jurassic) I went for, as I remember, years without Confession, though my sins were as Crayola Red. Now that I'm back in the fold, I find myself more and more aware of my faults.
Age does that.
Marriage, too... :o)
Because Catholic theology holds that Christ's shed blood / forgiveness only covers past sins. They were forgiven last week, but then they sinned anew. They will need forgiveness again this week, else (should they die) they will die in their sins.