If a dislocated shoulder can be dislocated again so easily, why don't doctors operate on it the first time?
Shoulder dislocations, particularly anterior dislocations have a high rate of redislocation among certain groups of people, particularly young, active adults. However, surgery for first or primary dislocations is still generally reserved for people who participate in heavy physical activity or sports activities. There is no general reason why it's done this way other than it is the accepted way. Surgery always has risks, regardless of the type of procedure and doctors usually try to err on the side of caution, using conservative (non-surgical) methods before surgery, if conservative methods are an option.