Because when you buy software, you know you are renting it - you technically can reverse engineer/decompile, copy, clone, resell - but you know you shouldn't.
If I buy a car and want to take the engine out, or a light and resell it - I would be very stupid, but, it is my property and I should be able to.
If Tesla want to lend instead of sell you something - fine, just be honest!
A functioning commercial regulatory apparatus would not allow vendors to call the practice of providing encumbered software licenses in exchange for money by the term "selling software". That we put to with this practice, which basically lives on consumer confusion, is a bug.
It's a lot like our allowing people to sell patent medicines as "supplements". In both cases, we let people distort the meaning of regular words for commercial gain.
Copyright is a very stupid concept. Just because we benefit from it doesn't mean that we should support it until the end of time. Perhaps we should start taking about getting rid of copyright.
Now, I'm not saying we get rid of all laws. End of copyright will not allow me to put a maliciously crafted copy of Microsoft Windows or Google chrome online in order to deceive users into thinking they are genuine. I still may not misrepresent when I copy things. In fact, I think these laws need strengthening which we can if we ditch copyright.
Vehicle makers are already starting to make that argument, that because they own the software, you can't do anything to the car without their permission:
