[ living on crumbs and scraping by your whole life and then going to a world like this, where water is just flowing, free and everywhere like it's nothing is almost an insult, to Wolfwood. Like he's being openly mocked for being so desperate his entire life.

it makes him bitter as the cigarettes he's usually grinding between his teeth, even if he knows deep down that it's somewhat petty and deeply childish of him. he doesn't care.
...or, at least, he's putting on a good show that he doesn't care.

and see, this is WHY his back is turned to Vash. He doesn't want to see that smile that somehow threatens to break down his defenses, that crinkle to the corners of his eyes that was so genuine in a way that Wolfwood has never been able to smile.

Vash can't make his judgements if he can't see his face!!!! ]

Ain't my business if they're suffering or not. Everyone's gotta keep a hold on their own shit, it's why we're all here, ain't it.
Trying to fulfill some selfish wish?

Least they can do is slow down and enjoy that they have anything at all.