Why won't the hitchhiker steal anything from the narrator?

The hitchhiker describes himself as a fingersmith, which is a euphemism for "pickpocket." The hitchhiker doesn't like to call himself a pickpocket as it's a word he associates with coarse and vulgar people who steal money from blind old ladies. As he explains, "fingersmith" is similar to "goldsmith" or "silversmith." It implies the possession of a certain skill or expertise, and the hitchhiker regards himself as a skilled professional.
The hitchhiker proves his remarkable skills by successfully relieving the narrator of several items without his knowing it. But he doesn't keep those items; he returns them to their rightful owner. As the hitchhiker explains he only steals from those who can afford it, such as rich people and winning punters at the race track.