As far as minimum wage not affecting us because we are ICs, yes, you are correct.
However, I can calculate my net and the driving time -- and believe me, I don't hesitate to tell a scheduler "That's less than minimum wage, and I don't work for minimum wage".
I AIM for about 2.5X minimum wage (which is $10 an hour where I live, so I aim for $25 an hour, net, after expenses).
I know shoppers who do much, much better than that, and others who complain "I can't make any money at all mystery shopping". A friend did 4 shops yesterday for $375. Much, much better than my $25 an hour! Actually, with reimbursements, her total was somewhere north of $400. Out here in the sticks, that's equivalent to a 40 hour week at a minimum wage job. And there are no jobs here. Not too shabby for one 8 hour day.