Why do christians do this..?

[Angrboda]

It's also worth noting that having such experiences isn't exclusive to those who believe the religious truths already. The behaviors, activities, and environment will induce the same altered state in a non-believer as a believer, as it is the behaviors doing it, causing changes in the body and the brain, not something metaphysical or supernatural. And because these altered states can readily lend themselves to religious explanations, and many of them include heightened sensitivity to suggestion, they are very effective means of turning non-believers into believers, and strengthening the conviction of someone who already believes (perhaps resulting in them being more religiously active).

I suppose it's possible to look at it as a form of cultural evolution in that, a church with these elements in their religious repertoire is going to succeed better than one without. So, perhaps, it's natural for such naturally mind altering methods and behaviors to come to predominate any religious community.

And regular churches aren't immune to this. There is plenty of mind altering stuff going on at a traditional church. Take a Catholic mass for example. Prior to the reformation, people would listen to the mass in Latin, yet only the priests understood the Latin. So what is the point in speaking to an audience of people in a language they don't understand? Any non-believer who has attended such a mass can attest that one doesn't have to understand the words for the experience to be powerful; it's perhaps more powerful because you don't understand the words.

I attended a Unitarian Universalist church for a while, and while different UU churches vary, most such churches have the religiously Christian element drained out of their worship/practice, to the point that it can be an almost purely secular experience, cohering around shared values like "growth" and "independent thinking" rather than beliefs. The church I attended is considered one of the most atheist of the UU churches in my city. Yet, even there, one finds that they have hymnals, and during church services they sing the lyrics to these hymnals to traditional musical accompaniment. Beyond it being somewhat creepy, one has to ask why a communal meeting which has become essentially completely secular has retained such a ritualistic element so closely associated with religious belief. I think the foregoing explains why.

(One might also ask why church services historically were held early in the day rather than later. I don't know if there is a historical reason, but it seems all too possible there is a psychological one related to the way the mind's behavior is different at different times during the day.)

Note also that the contemporary phenomenon of mega churches are essentially finely tuned, on-demand revivals, recreating many of the psychological elements of the old time religious revivals on a weekly basis.