A major reason is alternative social media platforms that will compete with it more effectively.
I've already mentioned Jurafide as one alternative for lawyers seeking American clients, and Jordan Furlong has mentioned LawLink just over a year ago. At that time, LawLink was restricted to American attorneys. It has since opened up to include lawyers from the UK, Canada, and Australia.
However, they still have a statement under the "threat of perjury" that the registrant is a practicing attorney in those countries. It was effective enough to deter this law student from registration.
I'm trying out Lawyrs instead, a platform specifically intended for lawyers and law students, with no geographic constraints, and more importantly, no threats of legal prosecution.
The ability to dialogue and network with legal professionals from 128 countries (although mostly American and British) is fascinating. They obviously have groups like other social networks, often comprised of alumni or interests, and a legal news page. But without RSS for the news, I'm unlikely to check in regularly on the site for updates.
There's also a page for law firms, and if the view stats are any indication they appear to be used with some frequency. Firms can provide news stories as well, and this might be an inexpensive alternative for law firms to send their releases.
Finally, Lawyrs has a publications page, which might be useful if you're looking for a legal scholar in a specific area. Publications give a lawyer credibility. But it's also a useful outlet for publicizing your publications, instead of remaining unread by anyone other than the editors of the law journal. I'm trying out different platforms to share some of my own recent publications in hopes of getting the material to people who might be interested in it.
A drawback of the site is the inabilty to import contacts like other social network platforms. Nobody with a sizable addressbook would attempt to manually invite all the lawyers in their (virtual) rolodex. I have no idea if anyone else I know is using the site, or really how useful it's going to be in the long-term. If you do sign up though, please do add me as a contact so I can see what you're up to.
One thing is for sure, we will continue to see more and more law-focused social networks. Eventually one, or several, will emerge as dominant, depending on the purpose they are being used. It's also possible that none of them will thrive, and the lawyers will instead flock to whatever networks everyone else is using. We're surrounded by lawyers every day, all day, and keeping in touch with all the other people in our lives is important.
It's also worth noting that a social network exclusively for lawyers doesn't allow lawyers to interact with past, present or future clients. More importantly, those potential clients can't find you, no matter how many news stories or publications you upload.