I think this is an excellent topic to discuss, realistically, Spectrum. Some Witnesses know quite a few Scriptures off the top of their head. Are they the rule, or the exception? The implication of your mother's comment is that they are the rule. It isn't true. Those who have applied themselves to study more than the average JW stand out in this respect.
The average JW does not prepare for meetings, gets less than 10 hours in the ministry (and counts more than they actually get), uses swear words when out of knowing earshot of other JWs, dishes gossip and dirt about other JWs, uses the contacts at the Kingdom Hall for business contacts (think Tupperware Parties, Jewelry Parties, Candle Parties, Pre-Paid Legal, herb businesses, phone services, etc.), does not consider the Daily Text, has developed great skills in slightly rephrasing what the paragraph just said into "their own words", does not know how to do research on Bible questions (elders have been instructed to help the flock learn basic research skills for a reason), does not keep their yard and home neat and tidy, does not bring up children according to the instructions in the Family Happiness book (the "upgraded" Making Your Family Life Happy), does not read well, and has not read many publications (in their entire life) aside from those considered in the weekly meetings.
That is the average JW. But, sitting in the meeting, you notice the ones who aren't average, and somehow believe they represent the majority. They are the vocal minority. Try this exercise: Go to a meeting. Sit in the very back. Make note of how many never comment once, struggle to get to the Scripture before it is read (much less comprehend or consider the context and application), fall asleep at some point, distract themselves by looking at their fingernails or doing some calendar planning, etc. It will give you an entirely new perspective on "the average JW" if your congregation is like any of the ones I attended.
Respectfully,
AuldSoul