There are many reasons for that. At the top of the list is that public relations professionals have more tools to leverage for their clients than do lawyers. No surprise, the outcomes can happen faster and bigger for public relations accounts than for those filing lawsuits.
The public relations industry can directly access the human being. Practitioners can appeal to all kinds of human emotions, for example. They range from the hunger for "what's fair" to what's seen as best for the next generation.
Lawyers, on the other hand, are trapped in the box of what's legal or illegal. The law is about the law, not about the abstraction known as "justice."Also, the law is open to myriad interpretations. It is well known that once you file a lawsuit you lose control. There is no certainty what strategies the opposition will use or what the judge and/or jury will decide.
Observe any public relations campaign. What's obvious is that the players will shift the strategies which aren't effective. On a dime. If the messaging in brandname media such as The Wall Street Journal and the "Today"show isn't resonating, they will take a deep dive into social networks. Yes, they will publish opinion-editorials on LinkedIn. They will also bulk up on placements for social media such as blogs. Several services have popped out which facilitate those.
The major issues of the day, be it reducing carbon footprints or dealing with addiction, will be primarily decided in the court of public opinion. The court of law will likely put the finishing touches on whatever the people decide. The American Revolution was started and fought via messaging, not legalities.