Most people just have no practice or experience writing. Asking them to respond to or write a large response to an email is a total non-starter for them. That's the default culture in the corporate world unless you have a strong company culture otherwise.
You know how popular grammarly and 2023-24 era chatgpt were? The prospect of writing an email actually makes most people quite anxious. They are not in the comments of hacker news, as a rule - they're watching YouTube and TV and don't read blogs. Just the way most people prefer to live.
There is somebody that I am having to work with right now that will not respond to a single thing I ask unless it is on a live phone call.
I will ask a relatively simple question via email, and then he will call me back an hour later and leave a voicemail just saying "Sorry I missed you, call me back" instead of even answering my simple question. I'm almost never at my desk, always running around out on the production floor (manufacturing engineer). I'll get his voicemail, call him back and leave HIM a voicemail re-iterating my question, and then I will also send an email again re-iterating my question.
We will go back and forth like this until EVENTUALLY we catch each other at the right time, then it's a quick 2-minute call. It takes days and days, sometimes over a week, to get one single answer that takes 2 minutes to talk over.
He is an external consultant I am working with, so I can't even just walk over to his desk. Absolutely infuriating. As soon as this project is done I am never asking him another question again, I'll find someone else. (I inherited the project and don't have the resources to find another consultant right now)
It’s about to get a lot worse too. Gen Z has had noticeably worse reading comprehension scores over the last 5-10 years and they are starting to enter the workforce now. Many prefer video over text and firmly believe that written text is “the harder medium”.
It blew my mind to enter college and peer review other people's papers. Up until that point I understood that there was a range of capability with writing, but I figured that in college courses the floor would be pushed up. I was dead wrong, and it was shocking to me that these folks had managed to get all the way through high school writing like 8th graders.
ETA: This is over 20 years ago, btw. I hear it's gotten materially worse. That terrifies me.