You sound like you're in a really lucky situation where neither your specific job, not your organisation has a big email culture.
But, for a lot of roles or organisations they use email for distributed tasking. Even in a reasonably small technical team I'd say this is common - so you start receiving email that requires response due to it either being a task or it checking on status on a task.
It becomes even more difficult in situations where your response is required quickly as business is being blocked while you don't respond. A lot of (for want of a better word) middle management roles fall in this category.
There is a bit of the 'hero' problem about email management and far too much "FYI"'ing but it is a real problem. Ultimately, the cost to "send" an email is a lot less than on the X people who you just asked for a reply. So in some senses the impression of zero friction communication is very costly.