Picture quality being oversimplified and reduced to “4k vs 1080” glosses over a lot of factors that determine overall quality of the presentation, which also includes sound.
Streaming involves a lot of things like compression and bitrate (and as a result bit depth) to be able to download potential 100s of GBs to even TBs of data that cannot be done in the present time. Blu ray has significantly less compression to fit onto the large capacity discs, and has better mastered sound (which in my opinion is still mixed horribly but that is another matter). Saying streaming is highest quality is like saying the 4k iPhone footage is equal to 4k footage from a Sony Venice camera. There’s significantly more to it than pure pixels. One looks like shit and the other is some of the finest digital video quality on the planet.
Additionally, movies available in any digital format are only as good as the available transfer of said film. If it is a contemporary movie, sure, the master file is widely available in the the original specs it was meant to be presented in. And it stills suffers from the downsides of streaming it. But for any older films, you aren’t watching 4k in the vast majority of cases. If they say that, it’s a marketing gimmick of “upscaling”, not 4k presentation. I’ve seen plenty of netflix and amazon older films that I know for sure were just the 720 files upscaled. Criterion, for example, a company dedicated to getting the highest quality transfers, has a very difficult time doing this for even renowned/ historically significant classics and has to work hard at it to do so, as is their model. We are talking about obtaining either maintained original negatives of films (very hard to do), or high quality prints, like preserved theater archive copies). In fact, streaming services saying most stuff is 4k is counting pixels only, not only ignoring all the other details that constitute a picture, but also ignoring compression frame by frame.
There’s a million reasons why owning media is better than paying a rental to stream a movie. I see only convenience and storage to be the selling point. As mentioned before me, owning the media cannot be understated in importance. Especially in the highest uncompressed format available in every case you can. There’s also the same benefit as there is in having a record jacket, a book, etc. Enjoying the poster, any other add-in’s, etc. Bonus features not available from streams, like featurettes or deleted scenes. But concerning the best transfers, such as Blu Ray criterions (which are both HDR and the highest quality one can see a movie without ridiculous storage capacity to watch a single film), you aren’t getting that same quality with compressed streaming. Also there are 4k blu rays. But just like we say in the movie business, most people wouldn’t be able to tell the difference between high quality uncompressed 1080 and even moderately compressed 4k anyway, let alone highly compressed. It’s so trivial beyond high quality 1080 when talking about viewing this on a home tv.
Just figured I’d put in my two cents as someone who both collects a vast array of physical film media and is a movie buff and as someone who works in this industry and knows a lot about this stuff.
I don’t care about the Disney product and think it is very overpriced, but if I were trying to get all the Disney movies in the highest quality I could, I would be buying individual, known source transfer blu rays of them all day. For both higher quality than streaming is and will be for many many years, and for the benefit of the physical media (it’s peripherals) and owning that film.