Statistically, someone, somewhere, has a VAX box that hasn't been rebooted since before the fall of the Soviet Union, running their org's MTA with a comically outdated cryptosuite. Anyone running vaxen that old is bound to be a regular here on HN.
Because email customers on all sides want email to arrive, there's little incentive to modernize configurations or requirements. When you disable ancient cryptography, you'll get blamed for your change making email from someobscurewebsite.gov no longer arriving. For a significant amount of mail servers, you can pick between "accept a random self-signed certificate using a cipher suite from the late 2000s" or "send email over unencrypted SMTP", and you just have to hope that the email server doesn't have your domain configured as "secure transmission required".
I'm in favour of Google just breaking the old, broken mail servers, but I wouldn't assume that TLS 1.2 is available on email servers.