Why?
Read this and it will not puzzle you again.
Democrat elected officials strive to please their voters, Republican elected officials strive to deceive their voters.
Elected officials of both parties share a generally negative opinion of, well, us. Democrats can brag about it, Republicans have to hide it.
Elected officials are, for the most part, either members of, or striving to be members of, the ruling class.
This has created a funny situation - in order to be nominated, Republican candidates have to conceal who they are and what they believe.