Shmitah, the most difficult mitzvah in the Torah, requires taking every 7th year off from work and having complete faith that G-d will provide. Yoval, after 7 rounds of shmitah, brings one to the 50th and highest level of holiness.

Rabbi Eliyahu Noson Silberberg explains that although we keep Shmitah to some extend, Yoval is only celebrated when the majority of Jews live in Israel. The only period in history that qualified for Yoval was the time around the first Holy Temple before the 10 tribes dispersed. When Moshiach comes, and reinstates kingship, builds the Holy Temple and gathers the exiles, we will once again observe shmitah and yovel in their entirety.