sort a linked list. convert an ascii number to an integer.
A lot of frontend devs don't even work with the DOM directly after having spent years with React. Could they do it? probably. Are they prepared for DOM-related manipulation questions on a whiteboard? nope.
And suppose there are a lot of cheaters out there who don't know the things on their resume, even including earning a degree without ever having to write a working program on their own. How would you screen them out?