There's an export contacts feature, which was restored after removing it resulted in a user backlash (http://venturebeat.com/2015/07/25/linkedin-brings-back-tool-...). But if a competitor tried to create a one-click feature for programatically exporting contacts from LinkedIn and importing them into their own database, they would probably get banned. And for the vast majority of users, explaining how to export/import a CSV manually is not viable.