Because it is not sustainable. I watch a lot of ball and I have never seen a team at any level play full court pressure defense for 40 minutes.
The most you will see is for a team to have one player pick up the PG at mid court to disrupt the offense sets. You will see some teams that try to apply pressure after made baskets but if you have a guard who is good at breaking the press, you wind up with defenders doing a lot of chasing for not any gain and your half court defensive sets are always discombobulated. Dawn is a great example, She presses like a surprise attack. Teams getting a little too comfortable bringing the ball up and then she blitzes them with a press (Or has one defender really hawk a key player from the mid court, as per SC's defense of Clark-- and even then, Clark still found plenty of space to work in).
I get what you are saying and I am not sure why some are spinning it as being anti-CKC. I am getting some of that too, We both agree that she is exceeding expectations to this point and has done great in her Assistant coach hires and bringing in quality power 5 players (rather than filling her roster with mid major transfers).
All of that is different is a different conversation from speculating about what her actual "system" will or won't be.