Tom Wingfield has a lot of reasons for wanting to leave home in The Glass Menagerie by Tennessee Williams. His mother, Amanda, is annoying and is constantly nagging at him about how he eats and what he does with his free time and money. She even returns one of his books to the library because she thinks he should not be reading it and she does not want it in her house. He finally explodes at her, reminding her that he is a virtual slave to his job, to this house, and to her.
It is true that that Amanda works, but it is Tom's salary which ensures that Amanda and Laura have a place to stay, and he has become resentful. He knows they need him there, but he has a wandering spirit (like his father) and wants to join the Merchant Marines so he can travel the world. In fact, his only escape is the movies, which is a poor substitute for actual travel. Amanda does not understand this need/desire (or perhaps she does and is afraid of it), and that only frustrates Tom more.
And finally, Amanda wants Tom to find someone suitable for his sister to marry. While Tom loves Laura, this is just one more reason to hate his life. He wants to do everything, but he is stuck doing nothing--or at least nothing he wants to do. In an argument with his mother he says:
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!... But I get up. I go! For sixty-five dollars a month I give up all that I dream of doing and being ever! And you say self--self's all I ever think of. Why, listen, if self is what I thought of, Mother, I'd be where he [his father] is--GONE! As far as the system of transportation reaches!
Again, Tom has plenty of reasons for wanting to leave. He is a grown man still forced to take orders from a nagging mother, he is working a job he despises and has to spend most of his money to help support his family, and he cannot pursue his own dreams because he is stuck being the sole support and comfort (of a sort) of his mother and sister. In the end, though, Tom does not justify his leaving with any of those excuses.
He tells Jim, his co-worker and Laura's gentleman caller, that he is leaving because
I'm like my father. The bastard son of a bastard!
His father, Amanda's husband, is an unseen character in this play, depicted only in a photograph hanging on the wall. Early in the play, Tom introduces him this way:
This is our father who left us a long time ago.He was a telephone man who fell in love with long distances; he gave up his job with the telephone company and skipped the light fantastic out of town.
The family received only one postcard from him after he left. It came from Mazatlan, and all it said was "hello" and "goodbye" and contained no forwarding address. We presume he had all the same reasons for leaving that Tom had: a nagging Amanda, too many unwanted responsibilities, dissatisfaction at his job, and the desire to travel. It is not particularly surprising that Tom wants to leave and that he does so in roughly the same manner as his father--without telling anyone.
When Tom tells Jim he is like his father, he is admitting that he is being selfish and inconsiderate of his mother and sister, but he intends to go--and he does. He leaves his mother and sister literally in the dark and sails away.