Why did shakespeare noble characters speak in iambic pentameter while commoners spoken mainly in black verse or prose?

Shakespeare wrote his plays in blank verse featuring iambic pentameter because that was the style of the day. I did not copy 5this i just guessed and used my knowledged.

“the first decision that led to brutus’ downfall is when he decided that he would join the conspirators in their plot to kill caesar. the plot did not work. the conspirators had to flee for their very lives. the second decision that led to brutus’ downfall is when he refused to listen to cassius. “ i hope this information you.