The question is do they ever wonder why they have never converted someone that really knows the Bible? That can quote scripture, that knows when then they use a verse that its out of context? Everytime they come over I leave them stumped with questions, why do they keep coming back? Is it because i came to a Wednesday service one night?
That's not accurate. Not a more common occurrence, but yes, I have known of people who know the bible and even have studied theology in college, and still became JWs.
Aside from what Wake Me Up stated, there are many other things to consider. Some people can go studying and discussing the Bible ad-nauseam, but they do not see the entire picture if they don't look closer to the real reason why people join the JWs, religion in general, or any groups for that matter. Most people don't join to learn something. Some people have been JWs for decades and still to this day can't articulate some of the things that they WT teaches based on their Bible. The reasons why people join have to do with what they feel, what's in it for them, not for learning about some mysterious Bible passage that has a lot of exotic meaning.
You are being too narrow in your assertions and questions. Aside from the Bible, look for reliable research that shed light about the real reasons why people join groups. That may give you a bigger/better picture.