Why people like to use the word bandwagon?

People 'like' to use it in the phrase "Jumping on the bandwagon" because it is a well known metaphore for going along with an idea, or forming an opinion by listening to others, and agreeing with them.

The expression 'jump on the bandwagon' most likely entered popular lingo during the middle of the 19th Century, as a reference to the colorful bandwagon used during pre-circus parades through host cities. Band members would ride at the top of these ornate carriages, accompanied by other performers or privileged local citizens. The parade route would soon fill up with curious spectators, with the hope they would later become patrons of the circus itself.