String problems are rare, though may come up more in search engine companies. But manipulating sequences comes up a lot in many contexts. Usually it's sequence

String problems are rare, though may come up more in search engine companies. But manipulating sequences comes up a lot in many contexts. Usually it's sequences of more complex things: instructions, packets, files, polygons. It's hard to assign tests directly on those, because you have to explain the objects themselves first. So it's a reasonable shortcut to test ability to manipulate sequences of characters.