I am definitely not an expert on US discrimination law, but I believe that is actually the case to some degree-many of those laws only apply to companies with more than 15 people (eg Title VII of the Civil Rights Act of 1964).
I know that some only apply once the company goes past 50 people; I was working for a startup as employee #4 and was looking at the rules for paternity leave (with respect to my then imminent second child) around the time the company passed 50 employees, and it at least kicked in some features of California law, if not Federal law.
Indeed, OSHA is another. That is why a lot of small businesses, mechanics and machinists for example, purposely stay small. They can't afford to grow because of the increasing regulations. There were several studies at the time of the early-1990s recession and again about the time of the dot-com crash about this, investigating the causes of "non-growth", because most new hiring usually occurs in mid-size companies. I don't really understand why anyone surprised that the economy (especially unemployment) is still screwed-up this long with the hammering mid-size companies have taken in the past decade.
