But in CJK countries, things were much harder and the entire I/O system had to be significantly more capable than what might pass for usable elsewhere. This meant larger ROMs, larger framebuffers, higher resolution displays, more complex keyboarding systems, the works. Everything was harder and more expensive for a long time. A common add-on was ROMs with Kanji (Chinese derived characters) support in the same way a person in the West might buy a new sound card or get a VGA card. Except this was just so you could use your new $1200 computer (in today's money) to write things on.
Back then, given limited memory, you also ended up with a ton of different display modes that offered different tradeoffs between color, resolution, and refresh. Because of the complex character sets, these Japanese systems tended to focus on fewer colors and higher resolution while the west focused on more colors at a lower res in the same or less memory space (any fans of mode 13h?). The first PC-98 (the 9801) shipped in 1982 with 128k of RAM and a 640x400 display with special display hardware. The equivalent IBM-PC shipped with 16KB of RAM and CGA graphics which could give you a display no higher than 640x200 with 1-bit colors but was mostly used in 320x200 with 4 (terrible) colors.
Even with similar base architectures, these formative differences meant that lots of the guts of the systems were laid out different to accommodate this -- especially in the memory maps.
By the time "conventional" PCs were able to handle the character display needs (sometime in the mid-90s), they were selling in the millions of units per anum which drove down their per unit prices.
The Japanese market was severely fractured and in a smaller addressable market. Per unit costs were higher, but the software was largely the same. Porting the same businessware to half a dozen platforms cost too much. So now the average user of the Japanese systems had a smaller library of software which was more or less a copy of what was on IBM PCs, on more expensive hardware -- market forces solved the rest.
(btw, the FM Towns, IIR, also had specialized graphics hardware to produce arcade-like graphics with tiles and sprites and so on, making it even more different)
Some of this history also informs why home computing lagged in Japan compared to the West despite having all of the other prerequisites for it to take off.
graphics
memory maps