Why did Ibn Mujahid limit [himself to] seven recitations of the Holy Quran?

The well-known seven reciters were not the only ones proficient (in recitation). Rather, their selection by Ibn Mujahid and others was to regulate the recitations and facilitate their memorization, by choosing an Imam from each region to which Uthman sent a copy of the Mushaf. Scholars before Ibn Mujahid had compiled books on recitations that included five reciters, following the number of Mushafs sent by Uthman. The assumption that the seven recitations are the seven ahruf (modes) in which the Quran was revealed is incorrect. As long as the sanad (chain of narration) is authentic, conforms to Arabic grammar, and matches the Uthmanic script of the Mushaf, then the recitation is acceptable, whether it is from the seven reciters or others. The shadhdh (anomalous) among recitations is that which lacks one of these conditions. The famous recitations are not limited to the seven; rather, there are other authentic and famous recitations that were rejected due to their deviation from the Mushaf's script or their transmission through obscure routes.