Not used responsibly? Hmm... I will rip a bluray disc, convert to HEVC while cutting it down to 720p with a low-ish CRF value (that is, low on the quality side, better for compression) which cuts down bitrate, and therefore the resulting filesize considerably. I've even done DVDrips in the same way (though I do not reduce the resolution of DVD video any) and my rips look perfect on a 50+ inch TV. Image quality is very much a concern, though, because I spent a very long time arriving at the process I use to transcode video to achieve the best results.
What about maintaining bitrate? If you have a 5000kbps video, and you have a new codec that can give you the same quality at half the bitrate, why not go with a smaller video? You can only push quality so much. There are a lot of "plebs" who would welcome a new codec that can chop bitrate in half without sacrificing quality. Ask anybody with a data cap and/or slow internet.
), because I don't like to produce garbage, and I know enough about that sort of thing to produce a quality result. There's no standard, no guidelines... if I wanted to I could capture a video of a cool base I built in 7 Days to Die for example, but upload a terrible 100kbps 320x240 video. Youtube also goes back quite a few years. Teamfourstar channel is a wonderful example of this. When they started DBZ Abridged, the audio sucked, the videos were small and of poor quality. As things went on in years the quality of their video (and audio) improved significantly.