Slow and calmeddown operators after front-striking era.
As Stickney proposed in his patents of US676208 or US889344, the risk to collide typebars each other was increased in change from up-strike to front-strike.
But the direction and the stream to change from up- to front- did not change and continued.
Without Stickney's patents of these execution.
Why? Visible, yes. But besides..
It was said. To strike keys in rapid one after another , would make collision or lead to the jamming together of typebars.
So why they do not jam so badly in front-strike era?
Because typist became slow.
Slow against quick or harry haste or rapid.
Even if the typing speed is fast, if the interval of sequential keying is kept enough, typebars do not collide.