Sorry for amateur question, but how/what does leaf shutter help/improve?
In this case we are talking specifically about strobe sync-speeds. With leave shutters, the shutter is in the lens, generally right in front/behind the aperture, and when it opens/closes it always exposes the entire sensor/film during a given exposure. However, they tend to be limited to slower max shutter speeds than a focal plane shutter. Focal plane shutters (such as the ones in basically all* 35mm and smaller format cameras) actually sit just in front of the sensor/film and during exposure it has 2 curtains, the 1st and 2nd curtain. At the start of the exposure the 1st curtain starts to move across the sensor. Depending on the shutter speed, the 2nd curtain may begin traveling across the sensor before
the 1st curtain reaches the other edge of the sensor. With a strobe, since the amount of time that the strobe outputs light is extremely short, may not expose the entire sensor if the focal plane shutter has the 2nd curtain begin moving before the the 1st curtain has reached the other edge of the sensor.
So, if you have a leaf shutter, you can use a strobe at pretty much any speed that the shutter supports. With a focal plane shutter, you can only use a strobe at the sync-speed, which tends to be 1/200s or 1/250s depending on cameras. It used to be even more pronounced, with sync-speeds of 1/60 or 1/125 on the earlier 35mm cameras.
* And by all, I mean the ones that the vast, vast majority of people will or have used