> Gmail is the most popular email service in the world
That's because it's been around for quite a while, and for a long time it was the best webmail service. It's also free, unlike most alternatives. And switching to a new provider means a new email address, unless you're using a custom domain with Google Workspace (or whatever they call it these days), which is a small minority of personal accounts.
(I gave up on Gmail a few years ago and switched to Fastmail, and like it much more than Gmail. But I'm the rare person who is willing to pay for email, and had been using a custom domain with Gmail, so my non-monetary switching costs were minimal.)
You're absolutely right that Gmail was the best webmail service when it launched, and for some time afterwards. How many people now commenting on HN remember when Gmail launched? Remember how revolutionary it was at the time? Every other email webapp, when you clicked on an email, would refresh the page. Gmail, when you clicked on an email, did not cause a browser navigation. It simply replaced the page contents with the contents of the email.
We're so used to setting webapps do this that we take this for granted, but Gmail was the first email webapp to do this. It's possible it was the first webapp, period, to do this; I feel like Gmail's use of XmlHttpRequest was innovative at the time.
Fast forward twenty years, and what about Gmail is innovative today? Nothing that I can think of. It's mediocre (there are lots of filtering improvements they could make that they aren't making, for example), and everything that made it good has been copied by other webmail clients. There's no particular reason except momentum to stay on Gmail.
Gmail spam filtering also used to be revolutionary and an unsung hero. I haven’t put effort into finding out if other options have caught up with that (because of aforementioned tedium of changing email addressed)
That's because it's been around for quite a while, and for a long time it was the best webmail service. It's also free, unlike most alternatives. And switching to a new provider means a new email address, unless you're using a custom domain with Google Workspace (or whatever they call it these days), which is a small minority of personal accounts.
(I gave up on Gmail a few years ago and switched to Fastmail, and like it much more than Gmail. But I'm the rare person who is willing to pay for email, and had been using a custom domain with Gmail, so my non-monetary switching costs were minimal.)