I agree, this has happens to me regularly. Someone reaches out on email asking for advice, I take the time to write a significant response, and get none in return. I've also found it discouraging as this kind of response is the most common I get. It's rare for me to see so much as a "thanks for the reply!" and rarer still to see an in kind response. I'm not very motivated to reply when I've been trained that they usually won't return the courtesy.