Winston actually answers this question as he thinks about the Proles. He believes that the only hope for rebellion lies in the Proles because of their number and often their physical strength. If a reader considers most of Orwell's descriptions of the Proles, they are husky-looking people who are used to manual labor, unlike the ministry workers such as Winston.
Unfortunately, the Inner Party has been able to convince the Proles that they are happy and that life is better now for them than it was before. Many of them are illiterate; so it would be of no use to try to disseminate print material even if it were done subversively because they cannot read it.
Here's the recipe for keeping people unattached, disorganized, uninformed, unmotivated, and afraid:
Physical torture: prisoners are isolated and beaten. Their teeth are pulled out. They are put in cages with rats. The Ministry of Love and Room 101 are the church and confessional of this dystopia. This society is geared only for pain and suffering.
Psychological torture: people are afraid of each other: anyone could be a spy. Cameras are everywhere. Parents are turned in by their kids. Women are taught to hate sex. No one is trusted. Everyone's addicted to gin and misery.
Institutional torture: there's no healthcare; there's no schools' there's not freedoms of speech; there's only war.
So, torture breaks the will of basic existence, let alone abstractions like rebellion. It tears down the body and the mind. Rebellion? What's that? It cannot even be conceived. The fatalism of 1984 does not allow for rebellion. If it does, it is solitary, harmless, and easily quashed.
To me, the reason for this is that the government in this society has so much more of a capacity to keep track of people than real totalitarian governments ever had.
In this society, the television screens give the government the ability to track everyone at pretty much all times. There is no way that you could possibly meet with enough people plan a rebellion.
In addition, the Thought Police are pretty much everywhere. So if you tried to start a rebellion, it's pretty likely you'd get one of them in with you and then you're doomed. It's sort of like how Winston and Julia are both rebels, but then they try to get in with O'Brien and it turns out he's with the Thought Police.