Etude, what I have come to learn is that people have needs, other than learning something about god, or the bible. Again, most people join religious organization because of what they feel, not for what they know.
People have other needs that may trump reason or doctrine. Some people need to belong to something, need to have some structure in their lives that they cannot come up with themselves, need a sense of community, need a sense of certainty, are too disappointed with the state of affairs in the world, feel like there are good role models to follow in the organization they join, feel close to other family members who are devoted to the church they go to, like the opportunities to socialize and events that they provide, feel that the church setting helps them stay away from drugs and other behaviors, or simply feel that the only way they can feels any spirituality is by having a community place where they can go.
The list of reasons are endless and VALID. In fact, JWs who join know nothing about what the WT teaches. They join because of what they feel. They learn what they believe later. Their feelings is what governs their decision of joining a religious organization.