In other words you think it's the threats...the threat of everlasting death, the threat of being cut off from one's family and friends, of incurring Jehovah's wrath and its consequences. Perhaps. Perhaps, too, some wives don't want to lose their husbands or vice versa, or their kids. And their dogs and cats.
It's true that all the above keeps some members active, but there are also people who use the Society to gain friends and prestige. Some like to live secure in the notion that they're of the anointed class, or that they're elders, or overseers, or even that they're known for their staunch defense of Jehovah-God and his earthly kingdom, and that everyone looks up to them for their encyclopedic knowledge of the Society and its doctrines. Perhaps they have every single publication ever to roll off the Brooklyn presses and they know people stand in awe of brother Knowital.
And others...just because they have nowhere else to go. Maybe they lean on the local congregation and its leaders for financial support, or that they are secure in the knowledge that people will always be there to visit them in their old age.
And finally, some people actually believe in it. They have looked at every doctrine and asked themselves, what other church has all the correct doctrines? Perhaps no angel from heaven has come down to call their leaders and give them authority from above...that doesn't matter. Using the process of elimination, they've determined that the Society is the only organization on Earth that teaches "the truth that leads to eternal life." They have a ticket to either Heaven or a glorified Earth and unless someone snatches it from them (i.e., disfellowships them), they will be left standing while fire falls from the sky and consumes EBT (everyone but them). Far be it from them to stumble this close to...well, you know. (It's just around the corner.)
There are, unfortunately, some "Christians" who believe that if people remain JWs, that they will lose any chance of everlasting life and be thrust down to an eternal Hell. I'm a Mormon and have been damned and denounced more times than I can count, and before that I was a non-denominational Christian. But I never believed that the Christian God would condemn anyone to an eternal Hell for their heartfelt beliefs. Nor for anything else, no matter how heinous. A person can go to Hell for any one of a number of reasons, but I believe that it's remedial in nature and does not last forever. The WTBTS condemns all non-JWs to eternal destruction, and thus use fear as a tool to keep people in line. So other secular Christians also use fear, just in other ways. Any sane person would be terrified at the thought of burning forever in a furnace of everlasting fire, ever burning but never consumed.
So yes, fear works!