In memory of Rabbi Levi Yitzchok ben R' Zalman Yuda Deitsch OBM
Why is Eicha (Lamentations) - the scroll read on Tisha B'Av to commemorate the destruction of the Holy Temple - not written on parchment as is the Scroll of Esther (read on Purim)? When Moshiach comes, Tisha B'Av will be transformed from a day of sorrow into a day of rejoicing. As every day we await Moshiach's arrival, making Lamentations more "permanent" by committing it to parchment is not really necessary and would imply that we had already despaired, G-d forbid. Purim, however, will also be celebrated in the Era of Redemption, and thus the parchment scrolls will also be used then.