Ben Drusai was one of the most influential figures in the history of halacha. His minimal contributions to the talmud grew over the years to entire sections of hilchos shabbos and there are even piyyutim composed in his honor such as
בן דרוסאי רדפנו אחריך להשיב לנו גזליך
ואמרתם כה לחי אדונינו בן דרוסאי
That being said, why do we not celebrate the yahrtzeit of such an important figure? (Fragments of these piyyutim were recovered from the Yehupitz Geniza containing most of the verses. If anyone thinks the verses would help answer the question, please comment saying so).