I think that most people search for happiness not because they are trying to find happiness but because they can't escape misery. If people would stop being miserable for 15 minutes by shutting their mind off then they would be happy - but most people simply don't know how to turn off their brain or to live for what they want to live for instead of living for what everybody else thinks is ideal.
I suppose there are many contributions to misery, but people would be happier if they simply stopped being miserable.
I know it sounds simple, and quite silly, but it's true. Stop trying to find happiness and instead work on not being miserable.