There are historical and cultural reasons for that. Even though hiragana can be traced back to the 5th century, the educated and elites continued to use kanji

There are historical and cultural reasons for that. Even though hiragana can be traced back to the 5th century, the educated and elites continued to use kanji exclusively until the 20th century, whereas hiragana was relegated to unofficial writing and it first became popular amongst women, hence gaining the condescending status of «female writing». Drawing parallels with hangul (as some have noticed) is not entirely correct as hangul entered the official use in the 15th century and has been in the extensive use for writing since then, even though the use of hanja has ceased only relatively recently. Hiragana entered the stage approximately four centuries later. Katakana, on the other hand, was developed by Buddhist monks in the 9th century to translate texts from India and later to represent borrowed words. The Empire of Japan used kanji and katakana in official documents. Then there is a distinction between the syllabary and vocabulary. Chinese vocabulary and pronunciation has entered Japanese in three distinct waves: go-on, kan-on and tō-on. The Tang dynasty kan-on wave was particularly and enormously important as it has supplied Japanese with a major new pronunciation system, vocabulary, administrative culture and literary. The earlier go-on wave is associated with Buddhist terminology that prefers the go-on readings, and the tō-on wave readings occur particularly in vocabulary brought through medieval and early-modern contact with China. Therefore, the same character can therefore contain several historical layers, for example: 明 has go-on myō, kan-on mei and tō-on min as in: 明王 /myōō/ historical layer: go-on, meaning: a Buddhist «Wisdom King» (such as 不動明王 Fudō Myōō) 明王 /meiō/ historical layer: kan-on, meaning «a wise, enlightened or excellent ruler». Even the pronunciation alone partly tells the reader which historical layer is being invoked. 明朝 is even more interesting as the reading of /myōchō/, being an older myō reading, indicates «tomorrow morning» whereas the /minchō/ reading, being a tō-on, indicates «the Ming dynasty» or related to the Ming dynasty. Neither hiragana nor katakana can preserve such details, and, depending on whom one asks, it may or may not acceptable to a Japanese national. Perhaps the younger generation cares less but it is not all that clear cut.