I do not think Newars are cowards. 
  But i know that Newari culture does not value  service and sacrifice as much as other culutures  do. And since business is at heart of their rich tradition, a career in defense or police force can be considered very risky with less reward. Historically Newari culture has failed to come together,instead they have split and fought amongst each other.
 But these are all general remarks, individuals are different. Hence these should be something to reflect back as history.
 The future for Nepali living together and prosperously is in our hand.  Let's make it a better place to live by joining hands.