Even some persons born into a rich family, yet they still need to work until they show themselves worthy before they can be allowed to become their own boss. Normally i don't see working for someone to be any kind of slavery because the employees was not force by the company to work for them. It was the person that took the decision on their own to submit application and resume, so that they can work for the company and the person still has the freedom to leave (resign) when ever they want.
Yes that's right because of their own desire to work in the company and they volunteer to get a salary to meet their needs, even so, it is far from slavery because everyone must work in their respective fields because they have ideals and hopes for the future that they want to achieve.