Most of us like to view people as 'good'. So, would a better question be: "Why do so called 'good' people legislate badly?"

We live in a nation "of the people, by the people, and for the people."  

Unless we've become much like so called 'communist' nations, of the 'dictator' variety, where the elections are fixed ...it is instead widely believed that we choose or 'elect' those who supposedly represent us.

So, why do so called 'good' people legislate badly?  My understanding of the question, inclusive of the answer to it ...is that they don't have a plumb line to judge 'good' by.