Wizards have an apparently trivial method of acquiring gold: Apparate into a bank vault, fill your Bag of Holding, Apparate away to Gringotts. It's doable by most wizards, carries no real risk, is unnoticeable by the bank, untraceable when they do notice the gold is missing, and the other wizards and goblins probably don't care if some Muggles were robbed by an unknown wizard.

My guess is that they actually do care, if only because they don't want Muggles getting too suspicious.

But yes, minor rights violations probably go on; the books note that dosing a muggle you have a crush on with love potion is seen as romantic.