They can and they should, but the world is not a perfect place, so backwards compatibility is neccessary.
So long as TLS 1.2 can still be used securely, its really not a big deal.
So long as TLS 1.2 can still be used securely, its really not a big deal.
True, but from a technical perspective "necessity" might be a bit of a strong term. For example as far as I know there aren't any Windows versions left that don't have support for TLS 1.2 but are still supported (i.e. not EOL). iirc Windows Server 2012 has support, but it's not enabled by default. So that's the closest to "unsupported" you get with Windows.
I think this is mostly because people are some what hesitant of enabling TLS 1.3. Because merely enabling TLS 1.3 along side TLS 1.2 can trigger latent bugs in clients.
I'm very doubtful. On the client side, people almost always go with defaults. On the server side, we are at ~75% market share for TLS1.3 https://www.ssllabs.com/ssl-pulse/
We are way past the point where people are afraid to enable tls1.3 because they think its buggy.