Well.. what is the connection between MIDI and probability? Usually musicians and sound engineers try to find flawless software and plugins with as much as precise timing and accuracy as possible. This one instead tries to skip played notes based on probability. Incoming MIDI message "note on" triggers the mathematics where user defined probability level decides will the note go through or disappear.
When it is useful? Well.. that depends. When I play layered instruments where one of them is kind of percussive or drums, I like to have that percussive instrument not to sound all the time.