Context: I recall a conversation on the edu-sig group (Python in education) about teaching beginners. I was arguing that, when teaching in visual-based environment (think Karel the robot or the turtle module), when introducing loops, it would be useful to have something like "repeat n: move()" instead of "for irrelevant_name in range(n): move()". (This is something I have implemented in Reeborg's world and that has also been independently added in TygerJython)
Someone (I believe it was Laura Creighton - sorry, I cannot find the link right now) mentioned that the very first example of loops they used was something like the following:
for letter in "some word":
print(letter)
If I recall correctly, quite a few other people teaching beginners also mentioned that this was one of the first, if not the first example they used. In fact, I think I was in the minority in not using this type of iteration over strings as an early example of loops.
So, I would argue that iterating over strings with beginners is something much more common than what you appear to believe.