Sending emails to your inbox is a dangerous default
One of the things I have to keep learning over and over again about email is that I should not let so many things bother me by showing up in my inbox. Even relatively low-volume things.
(I can filter or I can eliminate the email, depending on the situation.)
It starts innocently enough. You start getting some new sort of email (perhaps you sign up for it, maybe it's an existing service sending new email, or perhaps it's a new type of notification that you've been auto-included in). It's low volume and reasonably important or useful or at least interesting. But it's a drip. Often it ramps up over time, and in any case there are a lot of sources of such drips so collectively they add up.
In the process of planning an entry about dealing with this, I've come to the obvious realization that one important part here is that new email almost always defaults to going to your inbox. When it goes to your inbox two things happen. First, it gets mixed up with everything else and you have to disentangle it any time you look at your inbox. Second, by default it interrupts you when it comes in. Sure, I may have some tricks to avoiding significant interruptions from new email, but it still partly interrupts me (I have to look at the subject at least), and unless I'm very busy there's always the temptation to read it right now just so that I can throw it away (or file it away).
(Avoiding that interruption in the first place is not an option for two reasons. First, part of my job as a sysadmin is to be interrupted by sufficiently important issues. Second, I genuinely want to read some email right away; it's important or I'm expecting it or I'm looking forward to it.)
It's certainly possible to move email so it doesn't wind up in my inbox, but as long as the default is for email to go to my inbox, stuff is going to keep creeping in. It's inevitable because people follow the path of least resistance; when it takes more work to filter things out (and requires a sample email and some guesses as to what to match on and so on), we don't always do that extra work.
(And that's the right tradeoff, too, at least some of the time. One email a year or even a month probably is not worth the time to set up a filter for. Maybe not even one email a week, depending.)
If email defaulted to not coming to my inbox and had to be filtered in, my email life would be a very different place. There are drawbacks to this, so in practice probably the easiest way to arrange it is to have different email accounts with different inboxes that have different degrees of priority (and that you check at different times and so on).
(Of course this is where my email mistake bites me in the rear. I don't have the separate email accounts that other people often do; I would have to set up new ones and shift things over. This is something I'll have to do someday, but I keep deferring it because of the various pains involved.)
PS: There are also practical drawbacks to shifting (some) email out of your inbox, in that unless you're very diligent it increases the odds that the email won't get dealt with because you just don't get around to looking at it. This is certainly happening with some of the email that I've moved out of my inbox; I'll get to it someday, probably, but not right now.