It's one thing to choose not to respond to an email from someone you don't know. I can understand that inaction at one level, although I don't always agree with the practice.
It's a far different thing to choose not to respond to email from people you work with. I'm talking about individuals who work for the same organization as you. They may be peers, or direct reports, or supervisors. You may or may not know them personally. It makes no difference. You owe them the courtesy of a response. The failure to do so shows at best a lack of respect. At worst, it communicates a disdain for those who committed to serve the same cause as you.
Maybe you cannot respond right away. Perhaps you're not in a position to respond at all. That's okay. Let the sender know where things stand so they're not left in the lurch waiting for a reply. Recognize the absence of a reply may create difficulties for that sender.
I'm astounded that well-educated, "accomplished" people don't respond to email from colleagues. I'm even more astounded that such inaction often goes unreported and unacknowledged.
Unless we are accountable to each other as professionals, the work we do can be more difficult than it needs to be. That accountability starts with responding to your colleagues' email.