A few reasons:
1 - Education was different. Now they don't even teach decent grammar in school.
2 - There WERE people who just didn't "get" it - and they just never read the Bible.
3 - Language changes. I just read Bonhoeffer and even reading the letters that were written between him and his friends was a very different language than what we speak today. Yes, I know probably some of the letters were translated from German but there were letters in there written in English as well and I was thinking of just how differently they are written from what would be written today. There was a much higher level of language at the time.
We have a woman in our congregation who has learning disabilities. She reads at probably the 4th grade level but she does better if she can hear a book being read so she tries to get the audiobook rather than the reading book. The only audio Bible she can get right now is the KJV and she said that she just can't understand it. She's in her 50s. What should we do? Allow her to struggle and just not understand God's Word - or give her another version that just might help to bring God's Word to her in her own language? I'd say the latter just might be a little bit better.
Oh, I never said that other versions weren't useful. Your examples are exactly the reason! I just was making the point that people seem to think the KJV should just be discarded/retired/made obsolete because some people have difficulty with it. Your comment about education being different is very true. I work in a position where I interview for new hires. Reading through the resumes from college graduates makes me wonder how they ever got through junior high, let alone graduated from a college! Most of them can barely spell their own names!