I once heard from Rabbi Blum (possibly in the name of Rav Yaakov Kamenetzky) an explanation. The Sforno on the possuk "im yeheye Elokim imodi etc." says a fascinating pshat. Yaakov at that time was on such a high level that he begged from Hashem to be treated only with the midas hadin. He did not want to accept Hashem's boundless compassion. Hashem agreed and that is why it is found that Yaakov suffereed the most from all of the Avos.
This is why the tefillah that Yaakov instituted could not be a requirement on Klal Yisroel. The foundation of tefillah is compassion. We beseech and pray to Hashem for Him to shower us with His mercy. Yaakov who personifies midas hadin could not compel others to rely on midas harachamim.