Because, when someone has a heart attack it is due to a blood colt went up into their heart so in order to relieve it you have to thin the blood so if there are more they wont break off as well and go down to the heart while the person is having the heart attack because it will cause them to die. A stroke however, is when blood supply to the brain is interrupted or reduced. It deprives the brain of oxygen and nutrients, which can cause the brain cells to die.
