The story would be different because Tom would be away and doing what makes him happy. He might not drink or smoke as much, if at all. Laura might feel more comfortable with telling her mom she dropped out and she might be more accepting of her not meeting a man. She might feel that she can take care of herself.
The mom might encourage Tom to do what makes him happy, and not get so upset about him always being at the movies. She might even be okay with him drinking a little since she can't say the guy who left her drank often. Paura wouldn't have to go to the store to charge butter and have to make payments on the lamp if both the father and son had jobs, or the father had a good paying job.
I don't think I would like this book if this was all the actual book because it wouldn't have as much to wonder about, and there would be much less drama And it just wouldn't be as interesting.