what i actually care about is: - authenticity: that you sent the message, for some value of "you," maybe your email addy[0], - integrity: it was not altered (and, in this case it was, both headers and text, thanks to dmarc, mailmate, etc.), and - confidentiality: for some, not this, email privacy is needed
from my pov there is a serious disconnect here
On my small system I feel pretty much the way you do, but large systems have different issues. Someone will get a plausible sender to send them a message with spammy contents, then they will resend that message unaltered to a zillion recipients at large mail systems which is hard to detect quickly since the DKIM, DMARC et al. are all OK. Being able to see there is an extra hop or two in the path that doesn't look like a mailing list is useful for them.
and 30+ years of email content and protocol hacking driven by that view has worked sooooo well randy