The opening paragraphs about Rip give several adjectives that you could use to describe him. He is a simple man who doesn't need much. He is good-natured and gets along with just about everybody, and finally, he is kind. He is genuinely liked by kids and adults alike in the town because of how nice he is to everybody. Rip simply isn't a mean-spirited individual. He is also childlike and playful, and that can be seen in his willingness to assist the kids in sports, teach them to fly kites, teach them to shoot marbles, and tell them all kinds of great stories. Rip is also incredibly helpful. He's selfless in how much he is willing to do for other people of the town. Unfortunately, his work ethic toward his own life isn't as robust:
In a word, Rip was ready to attend to anybody’s business but his own; but as to doing family duty, and keeping his farm in order, he found it impossible.
As for what makes Rip this way, that's largely up to individual readers. His personality could be a genetic part of him that he simply can't help, or he could be the way that he is in response to something that he has seen growing up or been taught. Some readers even like to blame his wife.