Many things cannot be created individually, no matter how smart and creative you are. Think of pyramids, space ships, - or even GMail. It's about leveraging the resources of a big company.
And not to forget the low risk: you build something while you are on salary vs. building something for equity that may or may not worth dollars in the end.
Also apparently American-type slavery was a historical abberation. A typical slave in the past was not unlike a salaried employee today. He was well-treated, earned good money for his services and was able to free himself after accumulating enough of it, which is not unlike the FU money many a startup founder wants to have.
[0] - http://en.wikipedia.org/wiki/Egyptian_pyramid_construction_t...
If you don't think enslavement to a particular person is worse than working now, you need a reality check.
Also consider that technology sector is somewhat special in this regard. Your typical unskilled worker is pretty much a wage slave. Many a slave in the past (again, excluding US) was in much better situation than your average friendly neighbourhood supermarket clerk.
Unless you are using some exotic definition of enslavement, there is a fundamental difference between slave an employee. A slave is a property of his owner [0], thus slave has no agency and is completely dependent on her/his owner decisions. Employee may choose to be dependent on her/his employer to any extent she/he chooses, but it is her/his choice. You may argue that both slave and employer may end up being completely dependent on her/his owner/employer, but from the point of view of the law and society the situation is always completely different.
http://en.wikipedia.org/wiki/Indentured_servant http://en.wikipedia.org/wiki/Company_scrip http://en.wikipedia.org/wiki/Penal_labour [4] http://www.nytimes.com/2012/11/17/business/global/ikea-to-re... [5] http://www.reuters.com/article/2008/09/05/mexico-walmex-idUS...