You're right, but there is value in the community of accountability that churches provide. Fasting, tithing, charity work, and self-examination are objectively worthwhile, but not things I'm likely to muster up the will-power to do on my own, at least not regularly. It's like physical exercise: easier to get yourself off your ass when you go to the gym with a friend, or join a regular class.

Also, even though I don't really believe there's any "metaphysical hokum" going on behind it, I'm still moved (aesthetically, and -- dare I say? -- spiritually) by liturgy and church architecture. I'm sitting in the same place, while seeing and smelling and saying the same things that people have for hundreds or thousands of years. That's pretty cool, and I always feel better afterwards. So, even if I'm rationally convinced that it's a psychological (rather than metaphysical) effect, it's still worth doing.