When you buy a physical object, such as a home, a car, a shirt, or a smartphone, shouldn't you be be able to repair it, modify it however you want, use it for different purposes, loan it to friends, sell it to others, and so on -- you know, all the rights and benefits associated with the concept of private ownership ? And when you buy a software object, shouldn't you have the same rights and benefits?
I own my home, but I'm not allowed to pour oil on the ground even though it would only destroy my own grass. I own my car, but I'm not allowed to remove the headlights and drive at night. Exactly where we place the limits is up for debate, but I think I conclusively proved to everybody reading this that there need to be limits the only question is where.
Being able to repair things is very different, it is _in_ the common interest and likely against the interests of the manufacturers.