No, I'm sorry, but that is completely wrong - there is a huge difference between a piece of software and document: software has to be able to execute on the target computer, a document only has to be understandable by a program written for the target computer.

All Windows PCs use the same CPU and architecture (which is what I meant by target computer - not a specific instance of a computer, but a computer/OS type). Even modern Macs use Intel processors, which is why they can also run Windows. Xbox and PS4 architecture is largely similar, but the operating systems are fairly minimal and don't provide anything like the level of hardware abstraction that Windows provides - the games for those boxes are written as close to the metal as possible for maximum performance.

They don't run the same OS because they want to differentiate their (fairly similar) boxes and lock-in users onto one hardware platform - the boxes are generally sold at a loss in order to make money from selling games or licensing (basically, the razor blade model)

Windows software written in an interpreted language can run on different architecture target machine - but best of luck getting any fully compiled software written for an Intel chip to run on Windows RT, for example.

The issue around DRM is 99% around deterring copying. The fact this this patently doesn't work, and only inconveniences the customer, is something which content vendors are continually failing to realise. On some level, it's in the interests of both the IP owner and the content platform to continue with the DRM until the point that they believe the loss of trade from pissed-off customers exceeds the opportunity cost of people copying the content instead of buying it - once things get to those levels, there's an idiological battle as much as a commercial one which will take place between the publisher and the platform.

Ultimately, the only things keeping the DRM platforms alive are convenience of access (being able to load whatever you want at Comixology of Marvel Online, rather than searching it out on torrents or file-sharing sites), confidence in the platform (will the DRM content still work in the future) and the degree to which the customers want to stay legal.

The big problem for them, is that apart from the effort in acquiring the content, in most other ways, the legitimate content isn't a better product for more money, it's a worse product than the free alternative: your DRM supplier might go bust or exit the business, losing all the content you have paid for; the content maybe only works on one hardware platform; or the content only works while you have an online connection; or the content isn't available until later than the hard-copy product; or to use DVD example, the content imposes annoying usage restrictions - it won't let you see the film without watching ads for films you're not interested in and an anti-piracy message. Whereas the pirate content is free, can be kept without worrying about the platform and doesn't restrict how you use it. Morally, there's no contest, but in terms of value to the consumer, the pirate product beats the legitimate all ends up