Because the standards, as yet, are incomplete.
So far just the protocol and the USB implementation are there.
There is, for instance, no MIDI 2 file specification.
You can't recode a sequencer (DAW) unless you know how the messages need to be stored.
I don't recall reading anything that says that Steinberg's VST specification has been updated to include MIDI 2 messages either.

Standards as important as these take their time to define and implement, just like telecom ones.

It's quite possible that many manufacturers have deemed that the new messages are too complex for most commercial products.
They may end up only in top end devices.
It's a massive job too, to rewrite thousands of lines of code to incorporate all the changes.

Just a few thoughts.

I don't recall reading anything that says that Steinberg's VST specification has been updated to include MIDI 2 messages either.

Steinberg have made it clear that they will not be including MIDI messages in VST3. They expect DAW hosts to translate messages between MIDI and VST instruments.

I am disappointed in the OS vendors who have still not released class compliant drivers, despite the MIDI 2 USB spec being complete for almost a year now.

There is, for instance, no MIDI 2 file specification.

This is a big issue and I hope the MMA/AMEI release it soon.