From: Rabbi Mordechai Leib Winkler
To: Rabbi Yisrael Avraham Alter Landau
The responsum addresses the question of why the practice of holding the Lulav and its species during prayer, mentioned in Tur and Rama, is not observed even by the meticulous, considering that the Taz and Bach state it is only for the meticulous and for others it appears as arrogance.
Source: Orach Chayim II §170