The name comes from the fact that the keys S, K, and Y are under the user's fingers in the home row of the left hand.
The layout only has 30 keys, and since Japanese punctuation only requires full stops and commas, this means punctuation can be typed without changing keyboard layouts.
In addition, the lack of capital letters in Japanese means implementation is simple, since users don't have to press the Shift key at the same time as another keystroke.
It conserves keystrokes and also has a high ratio of hand alternation.
It rarely requires the use of the same finger twice in a row in a vertical motion so more text can be input in the same amount of time.