Tipping is a cultural aspect, not a legal one. Tipping was written into the law because people were already tipping, not the other way around.
People who dine at restaurants that likely commit wage theft might tip for moral reasons, but to me, it makes more sense to boycott those restaurants and communicate to managers and owners the reason why.
Workers being paid substantially less than their labor is worth by their employer is wrong.
Tipping just about doesn't in Australia, where we pay a reasonable minimum wage ($17.29 per hour for adults in full-time employment). You occasionally find people will tip a taxi driver or bartender, but by and large it's just not done.