True. But, at least for me, it's pretty easy to get distracted in a library or in a park. Plus, I think there's some added benefit in the fact that other people around you are doing the same thing (ie thinking about big/important stuff). You can kind of see the same effect in study groups or even incubators like ycombinator.
If the setting really makes no difference to you, I think the routine is still beneficial. Designating a time, every week (or day, or two weeks), going somewhere, and just thinking about life is a phenomenally beneficial exercise.
There's not much nicer in the world than sitting in a lawn chair on a hot tar roof in the middle of the summer with a gallon of water and a good book. I absolutely despise that my current place has a slopped roof.
Note that you can replace "church" with "library", "park", "rooftop", or any other place where you can be left alone in peace and quiet.