It happens to old keyboards or sometimes because dust or any insects mess with the interior of the keys. Sometimes its because you press it to hard and most keyboards have a gentle wiggly thing under their cap which can be easily broken, the keys are put to protect it firmly. Ushally RPG or FPS players might press keys out of anger. It's normal. You can live with it, or get a new keyboard. There are actually stores which sell spare computer pieces. That's cheaper.
