Most people really don't care, which is a shame. The sheer quality difference between a 4k digital movie and a 4k bluray is astounding. Hell, oftentimes a standard bluray looks better despite the lower resolution since it isn't being compressed
Isn't being compressed as much. All Blurays are compressed either with MPEG2, VC1, H.264, or H.265 if it's an UHD Bluray.
Video is really big. Compression was needed to make it even vaguely possible unless your quality was in the toilet.
HD-DVDs were smaller, so they were more compressed.
An uncompressed 24 bit 1080p image is just under 6 MB. If you save it as a compressed PNG, you cut that down to roughly 2.5 MB. Now, PNG compression isn't very efficient, and you can probably do some interframe magic if you really wanted to (cf lossless h264), but the whole exercise is mostly futile, since even if you cut your bitrate down to an eighth, you're still looking at, like, 20-ish minutes of runtime with 25 gigabytes.
Meanwhile, blu-ray looks as good as it does at an average of 25-30 mbit/s (0.03 gbit/s) (while UHD blu-ray even more so, with a better codec, so even more detail is preserved). The compression used saves so much space the trade-off is obviously worth it unless you're a production company making an actual movie, where every detail counts.
Another use cases seems to be archival of historical footage.
Both should use multipass ahead of time compression with a rate control algorithm, and both should have enough slack streaming bandwidth to handle complex scenes with buffering