People who write laws benefit from slavery and having lower economic classes. It was never their true intention to get rid of slavery, but only to calm the citizens that are rebeling against it. Overtime they figured smarter ways of slavery. Free slaves > but because of private property they now dont own anything still > they have to take any job under any working conditions > back to slaves again. If some escape this wage slavery, by not working or something, they make up a reason to arrest them, like vagrancy (illegal to be unemployed or homeless) or for not paying your debts or for some stupid reasons as drugs (planted by cops or not) or even dumber for resisting arrest even if there was nothing to be arrested for in the first place.