No, companies do change behavior. The public interest argument is:
1) Companies can make a lot of money skimming $1 each off of 100 million people.
2) Federal enforcement agencies don't have time or energy for that. We can outsource that to private firms
3) Private law firms can file class action suits, and companies are forced into agreements where they pay damages AND often need to change behavior
It kinda sorta works too, in that companies stop doing the bad things. Lawyers collect the lion's share of the money, but few consumers care about a $1 payout. Judges approve deals to make sure they're equitable to the class.
It sorta doesn't work, since settlements are negotiated by lawyers who don't really care about anything other than getting paid. Few actually care about the class they're representing. Judges are former lawyers, and part of the corrupt culture. So in many cases, the changes in behavior are less than one might hope for.