It's pretty rare when a modern timing belt breaks on its own. What usually happens is a component in the path of the belt fails, taking the belt off its path. This type of failure becomes a high probability when auto mechanics (or owners) go the short route and only change the belt leaving the water pump, idler pully(s), tensioner, etc. to go for another round of service life.
Good timing belt kits include ALL those parts. Some good timing belt kits even include replacement "torque to yield" (stretch) bolts which MUST be changed once the originals are removed.
Say what you want about chains, but poor maintenance practices to cut costs also cause failures in these systems. Even still, chains stretch and tensioners fail so they are not foolproof, especially when the WRONG spec oil is used when changing oil.