If Aristotle claims that part of the plot of a tragedy is suffering why do you think that people would want to view a tragedy?

Humans are thrilled and enthralled by the suffering of others. German even has a Word for it: schadenfreude. On some primitive level our reactions to the pain of others is probably a defense against our own vulnerabilities and fear of calamity. Our reactions to tragedy are manifestations of our desired indesctructability. Interesting too is the fact that an important element of a lot of comedy is pain.