Miracast turns out to be a terrible protocol in many ways. The way it uses Wifi networks is clunky, and requiring from-device streaming is fine for local content or screen mirroring, but terrible for streaming services (where you end up with Netflix streaming to your phone, then your phone transcoding and streaming to the TV via Miracast, which means two video streams on your Wifi and a lot of drain on your phone; by contrast, with Chromecast, Netflix streams from the internet to your TV with no intervening step).