anyone know why Earl always helps Joy

Some men do anything for the mother of their children. Isn't the producer Mexican? They have specific cultural beliefs about that.

Also, he might be a masochist.

More importantly, it might be more about not screwing up the kids' lives than about Joy herself. The best way to do that is by being an example to them, to undo all of the earlier harm of not just being a scoundrel but probably subconsciously treating them differently because of Joys infidelities.

He's trying to be a better person. Even mostly to those who aren't nice themselves. You'll notice there were other people who weren't nice to him or even kind of bad people, but he still helped them and still tried to be nice, though sometimes it was a struggle for him. Also while she is mean to him, he acknowledges that he was bad to her too, and has a lot to make up to her (regardless of what she may karmicly owe him too) and along the way of making things on his list up to her, he also doesn't want to add more things to his list.

To Love and win is the best thing. To Love and lose, the next best.

Like someone said, he's trying to be a better person. And at the end of the day, Earl does love Joy.

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WORDS MEAN THINGS! Also, before you come to bitch about a plot hole, rewatch the show/movie.

Joy also tries to help him out over the course of the show as well at times

Because she's hot and the show is much funnier with her in it.

Funny her name was joy. Yeah she screwed him over so many times. She is a terrible person. Getting knocked up by crabman when she was with earl.

Karma

The show wouldn't have been as good if Earl had been selective of who he was nice to. The whole point of the show was that he'd grown as a person. If he went round making amends only to people who he believed deserved it, he wouldn't be as sympathetic a character.