"The reductive answer to why TLS 1.3 hasn't been deployed yet is middleboxes: network appliances designed to monitor and sometimes intercept HTTPS traffic inside corporate environments and mobile networks"
From https://blog.cloudflare.com/why-tls-1-3-isnt-in-browsers-yet/.
They[*] still cannot intercept tls1.3 traffic and this is why Google doesn't turn it on in Chrome, Firefox (yes, some people still don't know that Google controls Mozilla fully) and Android.
* You can substitute "they" here by your favourite enemy or their combos: NSA, Putin, FSB, Trump, ZOG, GOP etc. Yeh, IT-hypocrites call them middleboxes.
Fuck, I love this shit.