The above post so cogently explains much. Just to add something, there seems to be a certain amount of emotional incest on the part of Amanda, who has too much involvement with her son's life in her effort to make him the supporter of the family. Emotionally, then, there is the Oedipal complex which exists in Freudian psychology.
This question could be answered from the perspective of the different aspects of the psychosexual theory of development proposed by Sigmund Freud. There are, indeed, a number of complex sub-topics within this theory that could apply to the play The Glass Menagerie.
However, the most obvious to detect is the paradigm of Ego Defense Mechanism, which is postulated under Freud's structural/topographical model of behavior.
Ego Defense Mechanisms are rampant in The Glass Menagerie. In Freud's theory, they include denial, displacement, projection, rejection, suppression, and rationalization among many others.
The fact that Amanda refuses to let go of the past shows denial. She also denies Laura's limping problem, Tom's lack of maturity, and even her role within the family. She does not accept the role of mother and protector, but passes it on to Tom. In turn, Tom suffers from the pressure under which he is placed, and Amanda continues to live her life obliviously.
Tom and Laura show suppression and projection: They suppress the stress that they live under by venting their frustrations on something else: Jim does it by going to the movies,drinking, and escaping from the house whenever he can.
Laura does it by projecting her personal issues onto her glass menagerie. It is clear that she feels as the piece that accidentally fell and broke. This is the way that she sees herself in a world that she cannot control. Laura's suppression is also obvious in her social anxiety and her inability to operate under normal circumstances. She cannot even hold a job, nor go to school. Her lack of self-esteem is extreme, and leads to her equally extreme behaviors.
Moreover, the family as a whole seems to be in a vicious cycle due to their general denial and supression. The turning point, however, is finally reached when Jim the visit that finally opened the door to their collective reality check.
It is through Jim, his composure, and acceptance of reality that Tom figures out how fictitious his life has been. It is also through Jim that Amanda realizes that there are no real prospects for her daughter. Finally, Jim gives poor Laura her ultimate reality check which is that her "prime" has passed, and he (her eternal fantasy man) is not available.
In the end, when Tom finally breaks free from the family, we see how Laura and Amanda are meant to continue to live the way they do. They will never see any changes coming their way.