The נסכים (libations) would not begin until the Yidden went into Eretz Yisroel, a full forty years after the קרבנות started in the משכן.
This מאמר explores why, using קריאת שמע and תפילין as the illustration.
In the מדבר they had only מצוות of רצוא and not שוב therefore they had no נסכים which represents the שוב. MP3
