That is not terribly surprising. There are several reasons for this.
(1) As others have said, Egypt "fits" better within The Standard Timeline of Western Civilization. This presentation of ancient history follows a dual history of Mesopotamia and Egypt before focusing on Israel and Assyria in the Iron Age and then jumping ship for Greece around the 6th century BCE. Achaemenid Persia consequently appears mostly as an enemy of the Greek city-states.
(2) As an corollary of #1, regions that are considered peripheral to Egypt and Mesopotamia rarely make much of an appearance in ancient history classes. Anatolia, with its rich history of successive empires, is rarely discussed even in Near Eastern history courses, and the same goes for Iran, from the Elamites right down to the Sasanian period. Poor Cyprus gets neglected as well, considered too Greek to fit within ancient Near Eastern classes and too Near Eastern to be covered in classics courses.
(3) It's a matter of pacing. Needless to say, it is difficult to condense 2000-3000 years of history into a single quarter or semester. It's not uncommon for topics earlier in the term, like New Kingdom Egypt and the Old Babylonian period, to get a large amount of attention while topics later in history -- the Neo-Babylonian period and Achaemenid Persia, for example -- are given short shrift.
(4) Textual sources for Persia are limited. Historians are heavily reliant on (rather biased) Greek sources, as Persian sources are limited to highly standardized royal inscriptions and economic tablets. Egypt, on the other hand, has yielded historical inscriptions, private letters, literary tales, prayers and hymns, mortuary texts, and so on. For history classes that encourage students to work with primary materials, Egyptian history is considered a more accessible subject.
Finally, every class will be biased toward the interests of the person teaching it. If an ancient history class is taught by a papyrologist, you're going to hear more about the Hellenistic period. If it's taught by a Sumerologist, you're going to hear more about the 3rd millennium BCE. If a Hebrew Bible scholar is teaching it, you're going to hear more about ancient Israel.