There are few instruments that switch gracefully between sounds. Say you are holding out a nice string pad while the band finishes out the song, and you want to blend into the next song with diffrent sounds with out a pause in music. Till recently there were few instruments that can/could do this without an effect processors glitch or the sound droping as soon as you press the next sounds in. With presets and a keyboard that doesn't glitch really makes a huge diffrence on stage especially when you are trying to play multiple songs without stoping.