Rain-making and then piling up lots of billable hours provide job security. At least for a while. Meanwhile, books are having a shorter shelf life.
And the old-line wisdom was that you needed a book as the "price of entry" to become a brandname in your field. It's been a long time since Alan Dershowitz leveraged that strategy.
Sure, a book can be the tipping force from being a comer to established. But, with so many other communications vehicles available, publishing a full-length book is no longer "required" in branding.
Also, it will be listed on Amazon. If it gets lackluster reviews or none at all and plunges quickly to 200,00 on Amazon, yes, that's public shaming. Do you want to risk that.
Not taking the book route is really not new. Activist Michael Moore might still be an unknown had his first big expose been in the form of the a book. Instead he used film.
"Roger and Me" made him. It was later that Moore knocked out books. But he had already established a following.
More recently, now with social media, an Everyman can become a star just by having the ability to get a following on one or more social networks and social media such as blogging. Many of them never did a film. Or published a full-length book. And probably never will. Abovethelaw's Joe Patrice is among them. His is an unique take on legal developments.
For marketing, yes, an e-book might be useful. For example, "What to anticipate about state public nuisance law." But don't get cute and make it 100 pages. Your potential clients will get steamed when they press "print" and use up all that toner for those 100 pages. Do 32 pages, with lots of graphics.