why do they...?

The word "Hamburger" comes from Hamburg, Germany; the inhabitants of this city are also known as "Pork Eaters" in German. In Germany, local traditional snacks are often named after the place of origin, like the Frankfurter (also known as a hotdog), the Berliner (a jam doughnut) or Thüringer (Bratwurst). In Hamburg it was common to put a piece of roast pork into a roll, called Rundstück warm, although this is missing the "essence" of the modern hamburger, which is ground meat. However, another theory states that in Hamburg, meatscraps similar to modern ground beef were served on a Brötchen a round bun-shaped piece of bread. It is said that German immigrants then took the Hamburger to the United States.

good question. it's made of beef so that's a little weird. but it originated in Hamburg, Germany so i think that's why they call it hamburger.

not sure but my son calls them "hamboogers" its so funny and gross at the same time!