how does tom convince Joe that a pirates life is better than a hermits?

From the text:

"As the two boys walked sorrowing along, they made a new compact to stand by each other and be brothers and never separate till death relieved them of their troubles. Then they began to lay their plans. Joe was for being a hermit, and living on crusts in a remote cave, and dying, some time, of cold and want and grief; but after listening to Tom, he conceded that there were some conspicuous advantages about a life of crime, and so he consented to be a pirate."

Tom manages to convince Joe that being a hermit and giving up all earthly pleasures (food, warmth, and companionship) doesn't sound half as good as becoming a pirate. Piracy became an adventure that had no plan. It also afforded companionship rather than isolation.