Although Yerushalayim plays a significant role in our parsha, its name is conspicuously absent. Yerushalayim is the focus of the beginning of the parsha, which repeatedly teaches that once settled in Israel we must perform all mishkan service exclusively in the "one city of Hashem's choice". Similarly, Yerushalayim is established as a central anchor of our national and personal calendar at the end of the parsha, but once again, it is referred to as "the city of Hashem's choice".
Our observation is underscored with a quick review of some of the opening pesukim of the parsha: "Only to the place that Hashem will choose from among the tribes...[may you bring korbanos]" (12:5) ; "[To] the place that Hashem will choose to rest His Name...[may you bring your korbanos]" (12:11); "Only to the place that Hashem will choose from one of your tribes...[may you do the temple service]" (12:14); "Only before Hashem can you eat [kodshim] in the place that Hashem will choose..." (12:18); "When you will be far from the place that Hashem will choose..."(12:21). The pattern closes the parsha as well as we are told to gather and celebrate "in the place the place that Hashem will choose."
Convinced that "the city" was unmistakably recognized by all to be Yerushalyaim by virtue of a long standing tradition born at the akeida, Rabbeinu Bachya, based on the Rambam in Moreh Nevuchim, explains the expedience of the silence. He reasons that the reduced publicity would somehow deflect a battle waiting to happen between our own ancestors or against one of the indigenous nations, all of whom would not easily cede Yerushalayim to another nation nor to another shevet.
The repetition of the phrase that actually highlights the omission may best be understood, however, through a careful reading of the halachic writings of the Rambam. In Hilchos Melochim, the Rambam bases the mitzvah to build and rebuild the Beis Hamikdosh on the pasuk, "l'shichno tid'reshu - you shall seek His presence." (This is surprising as it ignores the more obvious and concrete text, "v'asu lee mikdash -and you shall make for me a sanctuary", the very pasuk that the Rambam records in Hilchos Beis Habechira as the commanding passuk of this mitzvah.)
The verb "doresh - to seek" is introduced to us as the matriarch, Rivka, fearing the loss of the pregnancy for which she prayed for well over a decade, is beset by questions that shake her to her very core (Parshas Toldos). Rivkah then sets out, "lidrosh es Hashem - to seek answers from Hashem" or at least the guidance of how to live with questions. Apparently the Rambam understood that building of the Beis Hamikdosh is a collective act of seeking out Hashem for service, prayer, forgiveness, sanctity and even answers and strength. Possibly the defining role of the Beis Hamikdosh is that it is the destination for those individuals who are seeking sanctity, the rich blessings it grants, and the profound depth found in its ambience. Much as Ellul and the Yomim Noraim (see Rambam Hilchos Teshuva 2:5 - "dirshu Hashem b'he'matz'oh") provide for us the annual enclave of inspiration, introspection, and guidance, the Beis Hamikdosh would accomplish this in ways beyond our imagination.
Perhaps we can project from this Maimondean approach that the name Yerushalayim is repeatedly omitted and replaced as "the city of Hashem's choice" to communicate to us that Yerushalyaim and all that brings His presence palpably proximate must be sought long before it will be revealed. This teaching that kedusha can be earned through honest and earnest seeking can't be overstated neither as we personally engage the redemptive moments of Ellul and Tishrei nor as we nationally experience the redemptive process of our times.