Turns out, people lost the ability to have multiple profiles on the internet, and I think this due to costs. None wants to pay both to personal Gmail and to the business Google for Work, and if you have multiple identities, the bill goes up quite quickly, and the ease of use is nowhere to be seen.
I self-host my mail server, and I have a few domain names that all point to the same mail server via MX records in DNS.
I also use mail user agents that allow me to easily choose my From: when writing and automatically use the right one when replying. I think even Outlook can let you choose From: easily, but without that automagic trick on replying, you are bound to make mistakes, so this is important.
For completeness, I slightly customized my mail transfer agent configuration so that mails from owner@business.be and sexy@boy.be reveal nothing about their true origin.
I had this setup almost unchanged for many years, used it in my various businesses for quite a while but now, it's more of a relic and a source of pride for occasional bragging.
I've been thinking to get back into real entrepreneurship by providing advice on email handling, but even after ICC scandals this year, and all the press coverage Nicolas Guillou got, the strategy of vulnerable organizations is to wait out these problems.
I can understand them. They lost institutional knowledge and a lone wolf won't help revert all these decades of neglect.