[iso1631]

No, browsers won't do anything of the sort with HTTP. Or ftp. Or SMTP.

HTTPS sure. SMTP when they start a TLS session sure, FTPs too, there's protections at a higher level to ensure MITM isn't working, and you could probably argue that's a reason that DNSSec isn't required at all - after all get the wrong IP and your secure application won't do anything past the initial handshake. That's still leaking information though.

DNSSec, if used, is something that should sit in my DNS resolver, which should be part of my OS, not in my browser or ssh client - after all I might not want to use DNS, I might want to use a different protocol for resolving address lookups.