Companies like Symantec implementing devices like Bluecoat proxies are notorious for not doing their due diligence on their network stack. This ensures that it’s actually tested against devices and has the support of users to be fixed rather than a few developers who won’t be able to move the needle. At least that’s how I read this

I believe the point is to make it sufficiently widespread that an ignorant server developer can't ignore it.

(edit: or at least will start getting bug reports as soon as a Chrome/Chromium user enters the population)

We had tools for years that supported TLS 1.1 and 1.2 while large amounts of the web broke with them; merely having such tools doesn't make server developers care.

It's not about tooling or clients, it's about creating widespread usage by real users so that proper support can no longer be avoided or mishandled.