Imagine playing a series of notes all slurred. Your fingers move from the note you're on to the next note at the precise moment of changing notes. Next, remove the slur and play each note staccato. Unless you've been trained to use rhythmic fingering, you will likely notice that your fingers move early, in anticipation of the next note rather then waiting until the precise moment of changing notes. Of course if you use rhythmic fingering, then your fingers will move exactly the same way they moved when you were slurring.
As K.David Van Hoesen used to say, many difficult passages can be smoothed out with a rhythmic approach to fingering. It certainly reinforces rhythm when tongue and fingers are synchronized. Besides, it's awfully hard to imagine a valid argument in favor of haphazard movement of the fingers. How can that possibly lead to clarity and rhythmic accuracy?
"Obviously in slurred passages the tongue and fingers must be coordinated, but in separated note passages (tongued passages) the same coordination between tongue and fingers should be present, but often isn't." - K. David Van HoesenFinger/tongue coordination is a consciously developed habit. When fingerings and tonguing are both rhythmically conceived, they will always coincide. If my students have trouble with tongue/finger coordination in a tongued passage, I instruct them to play the passage all slurred, thereby establishing rhythmic fingering. Once the passage is rock solid all slurred, then the articulation is added. This method works amazingly well.