My advice is to be certain these characters show up again, either as characters or as something else --like an idea, a value, a representation of those characters.
I always fall back to Luke in Star Wars as an example. We meet his aunt and uncle in Act I. They die and we "never see them again."
But their deaths meant something--their deaths were the inciting incident to allow Luke to finally leave and join the rebellion. And, the characters were brought back in the prequels.
There are many ways to give the reader some reason to feel their investment in characters was not wasted. It sounds as though your main character is ditching life and going for something else. I'd suggest playing with any of the following:
Have the MC refer to those jerks he never wants to see again, throughout the narrative. This way, the reader feels like he is still getting some value out of learning those characters.
Have the MC grow and change... and then halfway through the story throw one of those early characters back into the story... and flummox the MC. Make him question himself; his growth, etc. Because this person from his past has a big psychological impact on him.
Continue the pattern. Just embrace your choice. I'm certain a story can be written where the main character keeps ditching life and people--and eventually the reader catches on and knows that the people in this 'episode' are just the latest iteration of what the MC will abandon.
Don't name the people at the outset. Consider:
James spent every afternoon with his mother. She'd insisted on it--and he'd always acquiesced. Until the day he didn't.
That's very different from:
James spent every afternoon with his mother, Mary Todd. She'd begged him to do so--said he kept her from falling into the dark night of her own despair, her burden so heavy, the deaths of her babes. It was too much for her to carry, she said, and so he'd always acquiesced. Until the day he didn't.
Any of these ideas might get you started thinking along new lines. In aggregate. they suggest that the thing to keep in mind is what you are telegraphing to the reader.
Anything is fair game, but play nice unless you want people to turn up their noses.