In my more than fifty years of living as an American Catholic — a miserable sinner, but one who goes to church every week and is up on current events — I NEVER have heard the US Conference on Catholic Bishops issue a statement reminding Catholics they have a grave moral responsibility to attend weekly Mass and that it is a sin not to do so. Never. I’ve read statements about how we should give more tax dollars to “the poor”; how we should oppose the death penalty; how we should support “immigration reform”, etc. However, I’ve never read that we SHOULD go to church. Likewise, I’ve never heard any of my friends who got married in the Church report that when they booked the church, they were told, “If you don’t plan to attend Mass every week and to bring your children to church every week when you have them, you’re not welcome to get married in the Church.”
In short, the “barriers to entry” are much too low in the Catholic Church.
I’ve heard priests say it, but never all the Bishops as a whole Body of clergy.