I believe it has to do with saving face.

I've worked with mixed nationality teams at a certain 4 letter austinite corporation a couple thousand moons ago. One thing in common with my Asian colleagues back then (many of which i still keep in touch with to this day), is that they would usually refrain from saying things that could rock the boat or disappoint you. If they lacked knowledge for the task at hand, they wouldn't let you know. If they were late on a delivery, they'd insist it would be ready by a certain date. This led to situations where other regional managers would have to plan contingencies to work around the issue.