Why might I frequently have shoulder dislocations?

Laxity. Ligaments hold bones together. Some people have ligaments that are looser than other people, allowing for more movement in joints. This is when people are described as "loose-jointed" or "double-jointed". Other times, an injury may have damaged the shoulder joint, and the structures that hold it in place may need to be repaired. Best to have it checked out.
Capsular compromise. The joint capsule (which holds the ball and socket together) , may be compromised, and may require surgical repair. See an orthopedic shoulder specialist for an accurate assessment.
Torn shldr capsule. The classic injury with a shoulder dislocation is a tear of the capsule and ligaments off the front of the shoulder allowing the usually stable shoulder to repeatedly slip out the front of the joint. The structures may tear away from the bone or become elongated and stretched out. Recurrent dislocations may require physical therapy and surgery to create a stable fully functional shoulder joint.