Why are puzzles so popular?

Puzzles originated as useful learning aids to teach children basic math, as evidenced by so many puzzles centred on weights and measures and distances, all everyday topics and objects that puzzle creators were seeking to enlighten the solver about. They became more widely popular in the wake of the Industrial Revolution, filling up the additional time newly available to people. With the rise of crosswords, word searches, and, more recently, sudoku, they have gone mass-market and are available to almost everyone.