Well, you asked! Here comes an educational, if
There was an episode of "Project X," a TV show that documents small developments that made a big difference in people's lives, that showed the people in 1978 who made the conceptual jump from the typewriter model (select from all available characters) to the phonetic-conversion model (develop software to do the work of suggesting likely candidates from the user's phonetic input). That totally changed everything.
Up until that light bulb came on, most everything was hand-written just because Japanese typewriters were so impossibly clumsy to use, not to mention expensive, that people were like, "Screw this, give me a pen!"
It then took years to gradually filter through the business world as computers got cheaper. So unlike the western business world where there was a generation or two of typewriters between old handwriting and modern computer use, Japanese business worked on handwritten documents right through the 1980s, before computers finally took over.
As a side note, this is one reason that fax machines are still in common use even today; they established a serious foothold during that decade.