Why do writers produce tragedies?

My overall intention on reading is to further develop my knowledge on any give subject, and to be entertained,and also any possible other criterias that my mind may not conjure in it's weary state(u can fill in). But as I just finished reading a tragedy, it took me back to the unfulfilled feelings I have experienced with past tragedies. It again makes me wonder why such masters at literature such as Shakspeare would devote such work to a tale without happy ending? I mean on an overall scale of enjoyment tragedies and happy endings just cant compete, am I right??