You’re missing it. Check your textually-adept privilege.

Seriously. I’ve always been a very good writer but people in STEM often aren’t.

And then when it's face to face, you have people who aren't lingually adept, what then? Take someone who speaks English as a second language. They may not be able to process what's being said in a face to face as fast as the topic is moving, but in an email thread they can take their time to read it all, and compose a response (which may take longer for them due to English being a second language). It's not as simple as either of you make it seem.