Just like any other professional services firm, those in law need media coverage. That pulls in new business and reassures current clients that they are being represented by knowledgeable, influential professionals. That's different from the objective of "making headlines."
In his analysis of why and how law firm Dewey & LeBoeuf died, James E. Stewart reports in his THE NEW YORKER article "The Collapse" that chairman Steven Davis wanted to "make headlines." Here is an excerpt (sub. req.)
To some in public relations, that might seem a risky goal. After all, too high a profile could scare off clients and deter prospects. Also, the crowd, including those in media, is fickle. It could turn on the firm at any time. Who the gods wish to punish, they often first give headlines to.