Quality of streaming is adjusted based on the speed of your internet connection. Also, you can manually adjust the video quality of any video you're watching. Here's more info about other factors that determine video quality: https://goo.gl/Z1s2LP
Appreciate the info. Please send a feedback report directly from YouTube with these steps: https://goo.gl/WdI0BK . While every individual report may not get a direct response back, we do review everything and use the details to investigate and fix issues. Thanks!