I sometimes see tuplets in written music that don't appear to serve any purpose, where the duration within the tuplet is the same as the duration the tuplet occupies as a whole. For example, I recently came across the following:
Here, the tuplet is clearly meant to take a single beat (the snippet comes from a 4/4 piece), but 4 16th notes already take a single beat without the tuplet.
The first time I saw a tuplet of this sort, I assumed it was simply an oversight. However, I've run into a few similar cases since then, so I'm forced to conclude that it probably does have actual meaning.
What is the purpose of these apparently redundant tuplets?