I have always been puzzled by this question - not because it is a mystery, but because as a child (not of Chinese descent) the reason seemed ‘obvious’ to me, but I’ve never seen a reference that stated it plainly. I’ve begun to wonder if there wasn’t some cultural reticence (pre-dating the revisions of Mao’s Great Cultural Revolution) about discussing some of the more culturally coercive elements of China’s imperial past. However, my readings in Chinese history seem to have a similar plain-spokenness (and lack thereof ) as my readings of European history.
[Warning - WAG ahead]
My WAG (mentioned only because I hope someone will be able to point me at a reference to confirm or disprove it) is that the Shang dynasty [ca. 1600-116 BC] pictograms evolved to ideograms and logograms through the Zhou (and Qin) dynasties [ca 1100-200 BC] and settled into something like the present mostly logographic form in the Han dynasty [ca 200BC- 200AD] The Han had considerably larger scope and area of influence than the Roman Empire, and I presume that the scribes and messengers required to maintain such a vast empire would have imposed a de facto written standard among the literate class. Many local languages may not have had a written form, while others (like Cantonese) did, but the Han writing system prevailed, as the Roman alphabet did in much of Europe.
Under the Confucian social system of the Han dynasty, learning and ambition tended to center on the imperial seat, and fluency in the imperial script would have been as essential as Latin in medieval Europe. During the era of the Three Kingdoms (each claiming to be thr rightful successor of the Han) and especially in the reunified Jin dynasty, we could expect fossilization of the Han script as a symbol of the Han lineage. By the end of the Jin dynasty, the Han script had prevailed for many centuries, and its grip was secure. I believe that is why we call it “the Mandarin system” in the west: ‘mandarin’ is a Western term for the 9 highest levels of Chinese imperial officaldom. In general, Chinese (and other nearby, but linguistically unrelated languages like Japanese and Korean) tend to have distinct layers of usage that have no counterpart in Europe
[e.g. in Japanese, the spoken language is written phonetically in the hiragana “alphabet” (more properly a ‘syllabary’), sprinkled (optionally) with kanji (ideographic symbols adapted from Chinese), with words of other foreign origin written phonetically in katakana. Sometimes foriegn words were spelled out in ‘romanji’ (Roman alphabet) but not in common usage (it would require knowing the foreign language) Acronyms, like WTO or CIA, are more often written in romanji]
Local variations and usages eventually arose, of course, but since the script wasn’t a phonetic representation, as in Europe, the usual drift in the spoken language would have exerted far less pressure on the local script. Chinese reverence for the past and (by European standards) ancient writings would have further stabilized the script. The Chinese are more likely to routinely read texts that are many centuries old (I ching, etc.) while Chaucer (ca AD1400) is well-nigh undecipherable to most contemporary English speakers.
[/end WAG]
I believe that the mandarin writing system is generally considered logographic, because it is built on words (Greek: logos) - specifically symbols for short (mono- or bisyllabic) in Mandarin. This is why some Chinese speakers in this thread have said “Yes, the writing is the same but it is pronounced differently”, which might puzzle those of us who aren’t fluent in Chinese languages. Saying that a written European is pronounced differently than its spoken form would make no sense for a phonetic language (even one as quirky and idiosyncratic as English). However, I would argue, based on my limited understanding of the subject, that they could be more accurately called “ideographic” with reference to spoken languages like Min. Except for a small percentage of local variant words, they are not logographic to Min, but only to mandarin.
Of course that was just a childhood deduction, and many things I believed turned out to be wrong. I’d very much enjoy any links or other cites to the history of the Han character system - or correcting the ugly menagerie of misconceptions I’ve undoubtedly picked up over the years.