I absolutely do not understand why half the replies here are about why someone would have their email in their signature block.
First of all, while I don't do it, it is helpful to me. I use Outlook and on Mac you have to oddly double-click or something on the person's name in the From field to get their email address, then it is not really that easy to copy the address. It is very annoying, but Outlook is great for everything else, so I don't really complain.
Secondly, it's not really on-topic. This is about Apple's bug. I don't know if people questioning the signature block email are doing it because they are baffled or they are Apple apologists.
The problem that we have seen over the past few years is buggy Apple software. Nobody worries about little bugs here and there, especially on new software. It happens. No dev team is perfect. But we see stupid, easily fixable, easily discovered bugs in standard, old Apple software. Sure, the Apple mail client sucks, but this is the bare minimum kind of email client. It is a standard feature of operating systems for decades now. Why can't Apple get anything right?
I understand changing out standard OS software to get better third-party solutions. Its unconscionable that in 2022 I do not use the Mail app because it does not have basic features (I'm no longer speaking about just the bug) or that it has simple bugs that should not exist with rudimentary testing (now I am talking about the bug again).
Get it together Apple. Take a year to sort yourself out. We don't need new operating systems every year or huge new features that add minimally to our lives. Like stage manager. Neat idea. Wish I had a real reason to use it. But I don't. Would've loved the dev time to go from stage manager into something like Apple Mail.