And if you go to any large company, you'll find that it's the same there unless you're in the upper "employee" caste--you're working for a contractor company, and have the same bad deal.
For all the discussion of diversity, any pathway out is pretty much closed. Even if you're in a historically disadvantaged group, the large company doesn't want to set a precedent that would establish the contractor group as employees. So the large company will block training and advancement, extracurricular networking opportunities, etc.
And historically disadvantaged minorities will be overrepresented in the contractor group because of both economic and educational disadvantage.
And to throw salt on it, arbitration agreements that you are forced to sign to work will preclude you using a class action suit to try to fix it, like Microsoft's testing group did in the 1990s. (Thank you Roberts court.)