I'm not really surprised at how heavily linkedin is used. It's an easy check for companies to carry out, so they'll make use of it.

As a candidate spending a bit of time connecting to people on Linkedin can help your chances of finding a role, so why not do it? Obviously, some people will have other better avenues of getting roles, but it's one avenue that can be used.

Personally I've never used Linkedin to find a role however I do find it handy just to get an idea of who works where in the industry and where pepople I've known in previous roles work now.