I find that a lot of serendipitous connections are made on LinkedIn. People will see my profile and strike up a conversation. Seems to work OK for what it is. What it isn't great for is content. There's never anything remotely useful there, the whole feed is a weird corporate version of the self help section in a bookshop. A lot of stuff is written purely to get attention. But I also don't see the tradeoff in as poor…
I would guess the reason it exists at all is that someone at LinkedIn figured out that, by its very nature, their site does not generate regular or frequent user engagement. What need is there to visit the site except to update your information occasionally or at select times when you want to make a change to your job situation?
But if you're LinkedIn, you don't want to run a site that people visit every now and then. You want users coming back all the time. More 30-day active users is better, right? So you try to create an artificial reason for them to do that. And it must be job-related, because that's what your site is about. So random user-generated job tips it is.