Its a more Democratic way for the govt to be forced to follow the will of the people. The Prime minister cant just do what he or even his party wants for the duration of his term he need support of opposing parties and thus needs to grant some of their desires as well.
The US on the other hand, essentially elects a dictator for 4 years (consider the fact that no President was ever removed from office during his term no matter how low their approval ratings may have been). The President can pretty much do as he pleases (to a certain extent) throughout his 4 years no matter how unpopular they may be. Think About Obama’s possible kill list or Bush maintaining the IRaq war when it was wildly unpopular. In most democratic countries includig Israel Bush’s govt would’ve collapsed once the war was unpopular.