This shouldn't be a surprise. But the question should be asked, how many also do not know the Faith?   

Many of us who went through religious ed. in the '80s or '90s were not really taught what the Church teaches. Moreover,the Eugene Walsh/Rembert Weakland/Oregon Catholic Press version of the Mass obscures the sacred action to the point where it's not clear that Mass isn't a Protestant prayer meetin' with a symbolic meal tacked on, so even those who went to Mass every Sunday may not have a clue.  Some of us were fortunate enough to learn the faith as adult reverts.

So can we blame apostates for lack of faith?  If felt banners, sappy St Louis Jesuit music, the C.C.D.'s busywork in place of religious ed, and (most importantly) Christ with a de-emphasized cross coming to save Man who does not sin (Confession by appointment only!) are Catholicism, no.

And maybe we can expect it; if Mass and religious ed. are practical sins against the 1st Commandment, then apostasy is in some way right!