Depends. As a precaution. Any time there is a risk of a heart attack, they will give you aspirin. Different schools of thought will tell you different doses of Aspirin to give, so it is not definite that another person will get 4 baby aspirins if they have chest pain. They might get 1, 2, 3, etc.
For protection. Aspirin is known to have a cardioprotective effect in that it prevents blood clotting in the coronary arteries by impairing platelet function. So, when there is a suspicion that a patient might have a heart attack, Aspirin is given "just in case" until it's ruled out.