Some don't read the Bible . . . because they go to church! You might think that people who go to church are more likely to read the Bible and perhaps that is true for many, but there is a large group that attends church, but doesn't read their Bibles. Even though one survey reported that 75% of US adults say they have read a Bible passage in the last 12 months, only 21% of church goers read their Bible daily and 57% read occasionally or hardly ever. I think many of these don't read their Bibles because they believe they are getting enough at church. They may think that their preacher, pastor, or priest is telling them what they need to know from the Bible.
There are two big problems with this thinking.
1) Odds are the pastor has not read the Bible either. One survey suggest that only 38% of preachers study the Bible outside of preparing a lesson and some suggest, though there is no data to confirm it, that 9 out of 10 "pastors" have not read the entire Bible through.
2) Even if the teacher is well-studied and knowledgeable, there is not enough time in a short lesson of 20-30 minutes once a week to deal with much of the Bible. I know of one church that had a sermon that only had 1 Bible verse in it each week. At that rate they could go through the New Testament in 153 years. Got Bible questions? Ask me.