why do we blow shofar on yom kipur

the rishonim explain that we blow shofar on yom kipur to remember the yovel. the question is asked, if then we should blow only once every 50 years?
the sefarim answer: the concept of yovel is that EVERYTHING returns to its proper place. this doesn't only mean the slaves go home, but that in spiritual terms we are freed from being enslaved. if so yovel can be described as having a whole yar y"k. (this concept is based on the ramban on yovel)
this fits well with the famous gaon that if you count up all the yomim tovim you have 7. (2 pesach 1 shavuos 1 r"h 2 succos 1 y"k) and y"k is the shabbos (7th) of the yomim tovim as yovel is the kedusha of 8th after the 7 x 7 shmita cycle.