Assuming this number is accurate, I don't believe it has anything to do with comprehension of Scripture. You don't mean to imply that attending Mass is the prescribed way to learn Scripture? Do YOU?
Attending Mass is, if nothing else, a default way to hear Scripture. People should obviously study it on their own. But if they do not, or if they can not (think: illiteracy now and through the ages) by attending Mass they will be exposed to the teachings and stories of Scripture. As for comprehension, it is the duty of the celebrating priest to "open up" the Scriptures of the day by explaining their relevance to the audience.
The point that was being made was that a person who does not read the Bible on their own will, over a period of years, hear most of the New Testament and large hunks of the Old (thematically related, even) just by attending services. What readings to sermonize about is not left to the whim of the individual pastor. In any given independent Church there is no similar guarantee.
SD
What do you mean by "You are either in it (grace) or not"? Thanks.
I am sure I am not the best person to answer this, but I'll give it a go. People who consider grace to be digital (in or out, no inbetween) tend to view this age as one of "grace" versus the prior one of the "Law." If one does not accept Jesus then he is bound to obey the Ten Commandments and such and will be strictly judged for his transgressions. When one accepts Jesus Christ as their Savior, they are now considered "covered" by Christ's sacrifice and are in a state of grace. This means that their transgressions are not viewed against the Law and judged harshly, but rather their sins are forgiven when repented. Those living "in grace" do not fear being judged because they are assured that all they do is seen as the Righteousness of Christ.
SD