I don’t have notifications enabled. I triage the inbox 1-3 times a day, outside of checking for an expected email. Triage means responding then archiving, deleting, or snoozing. It’s pretty easy so I’m always baffled by people who have thousands of emails in their inbox. I get the feeling they just don’t take action or don’t receive any real communication.
Because it's easiER to have thousands of emails in your inbox.
Half-jokes aside, it's not as easy for everyone. I can speak only for myself, but maybe I can explain.
My mind abhors chaos, but it abhors dealing with chaos even more. It doesn't like dealing with emails, triaging them is a pain when I could be doing something interesting instead. My mind gets repelled by my email inbox, I have to force myself, and I mean FORCE myself to do things with it.
Then there's the chance of getting sucked in by an email that is not that important but takes a lot of time, but somehow my mind latches onto it and needs it done right now. So, even just dipping in for a quick check can escalate.
Some days it's easier, but it's heavily dependent of other circumstances that keep changing.
All of this (and more) makes it very hard to establish a routine around it. And because dealing with emails repels me so much, for work I usually go through periods where I start with a clean inbox, then stuff accumulates until I get fed up enough to put on my rubber gloves and clean it again. My personal email just accumulates.
That being said, I still get things done, of course. It just looks messy, which btw is very different from the code that I write and like to surround myself with, which is sparkly clean.
I hope that shines a light on why other people's inboxes might be different from yours.
I also find myself baffled by other people's habits and behaviors sometimes. I think these differences often boil down to that different people find different things easier or harder than others. But it's quite hard to keep that in mind, let alone what it might actually feel like to be in somebody else's brain.
For work, I'm pretty close to inbox zero... I'll mark unread if I need to followup and cannot at that moment, or if it's related to a yet-uncomplete task I'm waiting on from someone else. But at least once a week it's all empty.
I also tend to only check a couple times a day, and my personal email a couple times a week... similar no notifications. If it's important it will be IM, Text, or heaven forbid an actual voice phone call.