Radak (Shmuel II, 24:25, citing Shochar Tov 17): It is because they did not demand [to build] the Beis ha'Mikdash. They were punished even though it was not built and not destroyed in their days. We, that it was build and destroyed in our days, how much the more so (we must demand that it be rebuilt)! Therefore, they enacted that Yisrael pray three times every day for the return of the Shechinah and Hashem's Malchus to Tziyon, and the Avodah to Yerushalayim!