Because American courts have entertained utterly moronic claims for decades now and the DMCA eliminates any sanity in consumer rights around IP products.
When you bought a DVD, you didn't "Own" the movie, but you had a legal right to do things with that data you didn't "own" anyway, like format shifting and selling that physical object on to another person. You could copy that data off and do things with it. I think technically it would be a copyright violation to then put that movie file into Movie Maker and cut up your own personal highlight reel, but good luck finding a judge willing to hear that case if you don't upload it to youtube.
Now, thanks to the DMCA and courts being absurdly credulous of bullshit arguments from corporate attorneys, you no longer have basic consumer rights. If you try to even inspect the code that runs to protect your literal life, that can be a crime. You own the literal hardware, but if you try to act like you own it, that's a crime. You technically still have the right to format shift a BluRay for example, but bypassing the math protecting that data overrides that "right" and you are guilty of a crime. A CEO's wet dream.
If the DMCA was older, IBM could have prevented the existence of the Clone PC market and ensured a locked up market. We would all be stuck on absurdly shit hardware because that's what was more profitable for IBM.
Pre-DMCA, Sega was told that their trademark rights were overridden by the innate market right to interoperate with their product. IP rights used to be fairly weak! Sony could not prevent a company from selling a software product that ran playstation games. To this day, Nintendo simply pretends these court cases didn't happen.
This is part of why China has so much success in manufacturing and product development IMO. They don't need to develop purposely worse versions of things just so some other company can sit on their hands for 20 years collecting rent. If you want a fast moving market, the ability to lock things down for 20 years is fundamentally unacceptable, only enriching a few owners, and outright harming our country. Basically every time in history that IP rights are weakened or nullified, you see a burst of development and advancement in products and solutions.