Yes, people do pray to Kwan-yin for help, and Kwan-yin takes on whatever form is needed to be helpful. But while that story may present the hope of divine blessing, it is there primarily to show us what we should be. If Kwan-yin has a thousand arms with a thousand different skills with which to help others, we too need to develop a thousand skills with which to help others. This is the chief significance of the inclusion of the Kwan-yin chapter in the Lotus Sutra. It is there to encourage bodhisattva practice.
A Buddhist Kaleidoscope; Gene Reeves, The Lotus Sutra as Radically World-affirming, Page 194