In William's The Glass Menagerie, Tom's behavior is unacceptable. His family needs him, and society will be unable to care for them.
Tom has been abandoned by his father, as have his sister and his mother. Life is hard for him because he is a dreamer. He wants to write and spends his time at work composing poetry.
You think I'm crazy about the warehouse? You think I'm in love with the Continental Shoemakers? You think I want to spend fifty-five years down there in that—celotex interior! with—fluorescent—tubes? Look! I'd rather somebody picked up a crowbar and battered out my brains—than go back mornings!
His handicapped sister and his ineffective mother depend upon him, but he is childish—uncaring like his father: when things become difficult, walking away is the easy, selfish way out.
Laura is "crippled" physically and emotionally: she cannot function out in society. Her phobia makes her a prisoner at home—in a dream world. Amanda, Tom's mother, finds her greatest happiness reliving moments from the past. She is a nag, and she treats Tom like a ten-year old, but she does try to contribute by selling magazine subscriptions on the phone.
Besides the fact that the family is dysfunctional, the play takes place during the Great Depression. Finding another job may not be a viable option for Tom, but he is lucky to have work. Tom resents his mother's nagging, but he seems to care for his sister. The audience will begin to doubt this when Tom tells Jim that he has used the money for the electric bill to pay his dues with the Merchant Marines, motivated by his own self-centeredness. When Jim reminds him of the consequences—the family's loss of lights—Tom dismisses its importance: he won't know about it because he'll be gone.
TOM: [Finds paper.] Look—
TOM: I’m a member.
JIM [reading]: The Union of Merchant Seamen.
TOM: I paid my dues this month, instead of the light bill.
JIM: You will regret it when they turn the lights off.
TOM: I won’t be here.
It is hard to imagine a brother deserting his sister (and even his crazy mother) to a world in which they won't know how to exist. It is most probable that they will be thrown out on the streets for Laura can't work, and Amanda cannot make enough money to support them. Tom excuses his behavior, saying he's like his dad.
I’m like my father. The bastard son of a bastard!
I left St. Louis. I descended the steps of this fire escape for a last time and followed, from then on, in my father's footsteps...
Tom abandons the women in his life to find his own satisfaction and happiness. Ironically (and with poetic justice, as I see it), Tom never finds either of these things. He dearest wish is to leave his family his responsibilities to them behind; but at the end he speaks to Laura down through the years about his failure:
Oh, Laura, Laura, I tried to leave you behind me, but I am more faithful than I intended to be!
My worry is for Laura and Amanda; I have little sympathy for Tom. Walking away is easy. Staying when things are hard is what takes courage, strength and selfless concern for others. Tom leaves the women who desperately need him. His selfishness is a flaw in Tom's character. Tom had a choice be like his father or be his own man. Excusing his actions based on his father's choices is a "cop out."
Without knowing for certain what happened to his family after he left, and despite his regrets, I expect Tom will never be happy.