I can't speak for
@mintoots, but for me it's because I value the "end product" of what I'm trying to achieve.
Some of the best moments in my life have been when I worked with a team to execute and achieve something, and the fulfillment of the goal was what made it so awesome. It can be frustrating when one person prevents a goal like this from being achieved, even more so if the reason behind it is because they were being dishonest about something. Honesty, reliability - these are very strong values for me. Owning up to mistakes and putting others first.