Playing 3 separate bows per note on your arpeggio allows for more time on each note and on each string level. This slowing down of the speed of the string cross allows you to concentrate on the smoothness of movement. The next step of course is to play the arpeggio with one bow per note.
Notice how the upper arm begins to cross during the last note on the old string. If we wait until the note is finished then the string-crossing action will be too quick and jerky.