I realize that part of what you have stated is historically TRUE.  Only PART. 
The part that is TRUE is the part that when THEY do NOT cast their ELECTORAL VOTES the way in which their constituents have in-the-majority VOTED, then THEY should be VOTED OUT in the VERY next elections. Why?  
Because, THEY were voted into office to REPRESENT US. . . never, NEVER themselves. Their role is NOT to just vote, as you have stated.  

Their ROLE is to VOTE for themselves as a citizen of the USA.  Then, to again cast their additional vote called:  Electorial VOTE 

Oops!  Did you INTENTIONALLY forget your history lessons?  Or did you really THINK that I forgot the HISTORY of these United States of America?