Interestingly, there has been a lot of mathematical research on why people behave this way. When you break them down, you come down to having to decide whether or not to lie.  
 
What's even more interesting is that these research concludes that how honest you will be in the situations is dependent on the extent you believe the rest of the world is honest. It is disadvantageous in the situation to be honest if you believe that there is a greater chance of others lying to you.  
 
We may have moral standards, but those aren't always going to get us the farthest. Which is more preferable, of course, is a matter of opinion.  
 
Just my (mathematical) two cents.

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