Thanks to Kevin for his comments on "More on Church Planting":
Breaking free from our "isolated cultures" requires a lot of work and personal cost. It has been much easier to invest our time and money into a once-a-week gathering and then claim "over commitment" as an excuse to bow out of relationships that are outside the Sunday Service. Jesus principle of "where your treasure is there your heart will be also" could be applied here. We don't place enough value on relationships outside of the once-a-week gathering, therefore our heart is not in cultivating and tending to those relationships.
As I said this is not only a failing of the institutional way, but also my own personal shortcoming that I need to break free from.
Kevin has more to say at his website here.