Whatever happened to T-0

Watching a recent Blue Origin New Shepard launch and the engine did not start until T-0 with liftoff at T+9. Apollo and Shuttle launches had engine start prior to T-0 with full thrust and clamp release right at T-0 ( especially shuttle as once the solids were lit you were going like it not). So what is with these new rocket companies and never knowing exactly when the thing is actually going up?

 

Either. Liftoff used to be at T-0. Now it’s sometime after, several seconds or more.