Q.) what is the reason people have OCD?

A.) It's a coping mechanism used by the brain to calm yourself, and relieve stress. It's called a faulty association. Just like in a tramatic situation, if you are on an airplane and it was about to crash, you just grab a bad and think its a parachute, but it's just a backpack, you are dealing with the percieved emergency in the wrong way. Just like that a person with OCD doen'st grab the parachute, they grab the backpack and most times, it feels like OCD just creeps up on you because in that moment when you grabbed a bad, you were in the heat of the moment in your emotions and were not thinking clearly.