Commas used (with no conjunction) to separate a series of words. The parts are emphasized equally when the conjunction is omitted; in addition, the use of commas with no intervening conjunction speeds up the flow of the sentence. Takes the form of X, Y, Z as opposed to X, Y, and Z.
"Be one of the few, the proud, the Marines." Marine Corps
"We shall pay any price, bear any burden, meet any hardships, support any friend, oppose any foe to assure the survival and the success of liberty." John F. Kennedy
". . . and that government of the people, by the people, for the people shall not perish from the earth." Abraham Lincoln