YouTube users who do not have a paid premium subscription have to view a lot of advertising content. In the future, it may be added that there is no possibility to view the video in 4K format. This is indicated by reports from members of the Reddit community who have already been offered a YouTube Premium subscription by the 2160p service to view the 2160p video.
Some free YouTube users have noted that they are now being asked for a bonus subscription to view 4K video. It appears that the video hosting is currently testing this change, but there have been no official statements on the subject so far. This may mean that in the future all YouTube users without a Premium subscription will be able to view the videos in the resolution no more than 1440p.