It costs twitch money to transcode your stream to a lower quality, so they only do it for channels with more viewers where it's cost effective for them. For smaller streamers, they should be lowering the quality of their stream on their end so that they can get more viewers. (He's not "Forced" into 1080p, he could stream at 720p or 540p or lower his bitrate if he really wanted to. It would just lower it for everyone)
It costs twitch money to transcode your stream to a lower quality, so they only do it for channels with more viewers where it's cost effective for them. For smaller streamers, they should be lowering the quality of their stream on their end so that they can get more viewers. (He's not "Forced" into 1080p, he could stream at 720p or 540p or lower his bitrate if he really wanted to. It would just lower it for everyone)