The arguement might be that they don't need it.

Email has been robust enough to survive this long as the default internet communications method, can have E2E added to it and can be used to send all sorts of data.

But the protocol isn't owned by anyone and this leaves the market open for all sorts of providers to provide choice to the user whilst working to the same standard.

Email isn't perfect and has the dark side of scams and spam. But WhatApp, Telegram and others are still open to scams. Indeed customers are less suspicious of IM platforms than email.