Because there is yet no proper for loop for argument packs or tuple-like objects, fold expressions over the comma operators are unfortunately the next best thing.
Edit: also the default comma operator discards its lhs, it is pretty much always used for its side effects.
Yeah, I figured it might not be currently possible. I was thinking about something like Scala HList[1], which provides a map/flatMap (which enables for-loop) method for tuples (among other functionality).
boost.fusion, boost.hana provide similar functionality (i.e. arbitrary runtime or compile time transformations over tuple-like objects) but they are relatively large dependencies and it is not worth it just for a tuple for-each.
Edit: also the default comma operator discards its lhs, it is pretty much always used for its side effects.