If you hosted your own email server, why would you need to be familiar with SES, especially if you've been hosting longer than SES providers have been around?

Like email, I run my own HTTP server, serving directly to clients. I know about Cloudflare just from HN threads, but have never used it or know much about that whole reverse proxy universe beyond the very low-level details from having written several reverse proxies myself.

Why would they? I’ve been running Internet servers (web, DNS, SMTP, IMAP, database) for about 25 years and until recently have only had the roughest idea of what EC2 or an S3 buckets are. It’s only because my employer recently started working with a new company that uses AWS that I’d have heard of SES. Also, I’ve no idea what the Azure equivalents are. If I ever need to know, I’ll find out but until then, ignorance is bliss.

Precisely those who run their own email systems have no need to know what SES is.