Puzzles are usually asked to see how you go about solving a tricky problem. Most companies avoid asking it, because most puzzles hinge on a single trick which can be easily missed by a person when he is having a bad or nervous day.
Anyhow, puzzles are still in fashion and are quite fun to do as well.
We have kept this topic as an optional topic which you can keep solving when you are feeling bored. We do however recommend you to go through all the puzzles to get a taste of what you might face in the interviews. And who knows, you might be lucky enough to encounter one of the puzzles you already saw here.
Happy Puzzle solving :-)