People get a lot of emails every day - some of them from commercial sources and some that they have subscribed to as well as from their colleagues and leadership people. So my (presumptive) conclusion is that they are too busy to reply to my emails when I want to know some information that they do not perceive as being important.
Not replying to emails in a timely fashion seems to me to be the equivalent of walking away from someone when they have asked you a question in real life. Now if that someone walking away says, I'll get back to you in a minute, or tomorrow, then I am quite happy to let it wait for a day or two, but not responding at all seems to say "you/your kaupapa are not important in my agenda."
But wait, I know that the younger generation prefer to communicate through text and messaging apps. The point is, how do you make carefully constructed text as succinct as you can? Ah, the secret is video perhaps? I am not sure what the answer is.