One of the common ways to get out of poverty in the past was indentured servitude. People would voluntarily sell themselves into slavery because it was preferable to their current "free" position. You can't eat freedom.
For instance, did the fugitive slave acts of colonial America cover white fugitive indentured servants? I'd presume no, although some other laws existed to cover them (I'm by no means an expert but some reading makes me think this.)
Racism must have been a significant factor in making the difference of slavery and servitude in the American colonies: actual slaves were of African descent, while indentured servants were European, and apprenticeship contracts covered young American-born people.
When we talk about slavery in Europe today, in realistic terms it is actually more resembling the indentured servitude contracts of America (debt bondage and enforced servitude) but illegal (if authorities find out, they work actively to confiscate any proceeds of such contracts from those who benefit). E.g. sex workers who are deceived to take some form of a debt bondage.
Where I see the word "slavery" used is however often about situations where employment officials assign some training or intern arrangements for people to get job-seekers allowance. It's hyperbolical, even if there might be something wrong with these arrangements.