Because Discoveryplus is a stand alone app ,and Roku controls all the discovery plus on the Roku app itself.i ran into the same thing with shudder ,on shudder through Roku you do not get the live channels,but on the stand alone shudder app you do,recently shudder combined all 3 of there live channels into one and raised there price a dollar a month,but on the Vizio smart tv thier shudder app still has all 3 live channels .i bought the Vizio smart TVs because thier cheaper ,but I hook my Roku devices up to the TVs and watch my Roku devices,except for shudder and yes I can use my same email sign in to activate the Vizio shudder app.