Often DVDs and BDs have deleted scenes on them - but looking at them usually the quality is poor compared to the rest of the film. I understand that scenes are often cut before they hit post-production, so the colour/grading will be off, for example, and maybe they'll decide not to reshoot a scene so the acting and direction might be slightly-off too.
...but almost always other aspects are poor too, such as the film jumping around, the "resolution" being blurry (as though they used a cheaper or inappropriate film-stock), and plenty of dust/speckles and other visual artefacts that just shouldn't be there.
By way of example, see this deleted scene from Trainspotting:- compared to the opening scene - which still looks great today:
I can understand it's possible for post-production to fix the "jumping" issue (which would have been a lot of work in pre-computerized workflows) but how does the lower apparent film-grain size happen and the other aspects that aren't fully explained by post-production magic?