This is another one that's remained in the dance world for far, far too long.
You can't Rise if there is nowhere to Rise to.
At the start of a dance we should be standing tall and straight with knees not locked. Um, so how can we 'rise' at the end of beat 1?
Well we can rise, it's going to be foot rise which is incredibly difficult to maintain over the subsequent two beats (Waltz).
But if we lower first at the start of the dance
If we lower during beat one (bending the knees) we have plenty of potential rise through the rest of the beats of the measure.
And at the start of the next measure we 'fall' to repeat the cycle.
Hence it's Fall and Rise.
Other advantages are:
Checkout the /inside-the-steps section for more information such as why body rise does not exist