Moving past the simple

1-to-1 is unusual When there are more than two participants, there are typically two or more views of information. (This applies even among people with shared backgrounds and experience.)
Costs of agreement Bringing all of those divergent views together often requires a lot of discussion. Discussion, especially when conducted formally, is pretty expensive, and all of the beer required to soothe hurt feelings can be expensive - in both dollars and hangovers.
How much do you want the competition to know? When competitors (and even cooperators) meet to discuss how to communicate, it's not always clear where the boundaries of that communication are. One side may feel it needs information about another side's proprietary process, only to find a lack of interest in sharing.
Avoiding mediocrity Sometimes a lack of interest in complete communication can produce simple elegance; other times it produces a minimum set of features that needs to be extended for any meaningful use as an internal tool.