We wanted the system to remain fast and not use server for social login integrations. For example : if 20 users use Facebook login in your site at the same time, your server ( a single cpu) would have immense amount of work to do as it would make a hit to facebook and send in credentials, generate WordPress session cookie and validate for all 20 users. Also maintain other tasks going on in the site. As compared to version 4 browser only system, the WPLMS uses 20 client CPU's to make the hits and only make the single hit to the server for registration. Cookie less, Fast and secure.