Self interest is the name of the game in politics. If it's not we wouldn't be 20 TRILLION dollars in debt. We wouldn't be a divided country. 

After a politician gets elected their first priority is to get re-elected, ie self interest.

"The purpose of government is to allow for safe and peaceful co-existence..." Sorry, that maybe your view of what government should be about, but it's not what those in government believe. The purpose of government is to; 1) get re-elected, 2) acquire power, and 3) get re-elected.