Is there some reason that you are bound to do business with literal slavemasters? Are you incapable of resisting doing business with the lowest bidder?
Seriously, I can do this all day.
To address your question as why this is allowed to continue, you'd have to ask those within the US and countries that allow it to happen.
Australia addressed this in 1907 or so with the Harvester decision and other related law cases that became foundation to working conditions.
https://www.fwc.gov.au/about-us/history/waltzing-matilda-and...