Why don't other people subscribe to your religious beliefs (or lack thereof)?

[Mad Deadly Worldwide Communist Gangster Computer God]

Many reasons, but here are some from the viewpoint of a mainline Protestant:

1. Dule already crudely alluded to this in the OP, but culture is probably the most obvious explanation. Most Christian countries have become secularized over time and religion means far less to people than it did in the 1950's.

2. People don't believe that they need to follow a personal being or entity or have their transgressions atoned for by the Blood of Christ.
2a. People do not agree with the Church on sin or that certain things should be considered sins or moral errors.

3. Science has replaced religion in the minds of those who see religion primarily as a way of explaining the origins of the universe.

4. Mainline Protestant churches have adopted a wishy-washy theology and messaging that does not compel people to make changes or sacrifices in their life and build a transformative relationship with the Holy Spirit, and so they see no personal incentive to join a church as opposed to sleeping in the extra hours on Sunday mornings. The most fundamental tenet of Christian belief (John 3:16) has been downplayed or forgotten.
4a. On the flipside, conservative Christian churches' persecution of LGBT people and the downplaying of marginalized groups has colored the perception of all Christian faith traditions in a negative way.

5. Wholesale rejection of metaphysics and the value of prayerful contemplation of Scripture.

6. The underlings of the world fail to recognize my superior intellect and the rejection of progressive Anglo-Catholicism is evident of that. How I pity them. _/s