Why is "peace be upon him" said when Prophet Muhammad is mentioned, while "peace be upon him" is said when other prophets are mentioned?

It is prescribed to say "peace be upon him" (صلى الله عليه وسلم) when mentioning any of the prophets, and this is not exclusive to our Prophet (peace be upon him). Indeed, consensus has been narrated regarding the permissibility of invoking blessings upon the prophets.