Mavericks said:
But why the official SW Blu-Ray is 1080p (as well as majority of other movies' releases)?
Other Blu-ray releases often have enough effective resolution to justify a 1080p encode. This is not the case with the Star Wars Blu-ray.
The Star Wars Blu-ray is encoded at 1080p, yes, but that doesn't mean that the screwed-up 2K 2004 Lowry master they used to produce it requires that much resolution. Harmy's experiments show that very little detail is lost in downscaling it to 720p.
1080p is not magically better than any other resolution. Upscaling an old DVD to 1080p doesn't magically make it look better, for instance, and is only justified when you're using a TV that exhibits terrible motion resolution when displaying non-native resolution material.