Likewise, gmail would be totally useless if it was actually centralized and you couldn't email non gmail users.

But they can’t necessarily email you, given Google’s procedures regarding “spam”, i.e. anything from a small email server.

This is true. My last company used fastmail, but one guy insisted on using Gmail. Sometimes fastmail didn’t arrive at Gmail. We (tech team) said, this is a problem with gmail. C-suite said this is a problem with fastmail.

And so the word comes down, we have to move to Gmail. It’s believable decision making, but that’s how it works.

Though that's basically Google (and other large hosts) breaking the decentralized nature of email in their "effort" to combat spam.

Google isn’t as bad as Microsoft or AT&T in my experience. My personal server now is working fine with those now too.

Yeah, that's my experience too. Google doesn't like new domains, but at least accepts mail and delivers to spam (or to the inbox once the domain is old enough). Microsoft just refuses all mail if you host on a VPS whenever someone else on the block (NOT the same IP) misbehaves (or is accused of misbehaving, not sure).

Yet my bank(s), linkedin, netflix, microsoft and a bunch of mailers all had message arrive in my inbox this morning.

I work for a 100-year-old company with 30k employees. Last year we moved from self-hosted Exchange to GSuite, because it's just easier to spend money on that than to spend money on an increasingly complex and hard-to-staff-properly internal service.

The issue is not self hosted versus GSuite. It rarely makes sense for any company to self host their own email. I think the parent poster was saying few use Gmail versus hosted outlook

My 40 year old company with about 12k users switched from self-hosted Exchange to Azure-hosted Office 365. I'm assuming part of the reason for this is to ease complexity, and it's working quite well for us.

Companies like hosting their own email. Users don't because because they don't have an IT department whose job it is to filter spam etc.

I'd argue the trend is that most companies don't. They host it with a custom domain on Google Workspace or M365.