I connect with colleagues, even my manager when I was at my previous job, even though I found my current role on there.
But, think about it from the current plays - they have the work connections (organic "company graph"), the user's skills, your current job details (think about both of those as being an HR play), a learning platform (Lynda, but think of that as internal training/cloud qualifications), industry/enterprise trend information (can dive into the data of all of the roles and build products based on predicting market requirements). Slap on Pulse and SlideShare as publishing and an established (and probably growing) revenue hose from Recruiter and it makes some sense.
