Hardees (which was my first job, in 1973) is frequently found in small southern towns with limited opportunities for employment. Fact is, where I worked it was the only fast food in town, years before any other.
The poor, especially before the mid-90s (and the emergence of the internet) simply had no knowledge of the opportunities for justice. And even after, they lived in a society (often southern and poor) where sexual harassment was often the norm. (Not right, or accepted by women, but a very regular occurrence.)
And as far as class action, “The poor have lousy lobbyists.”