Yes, yes, we all hate DRM. Cars are more complicated: you don't own the air that goes in one end and and comes out the other, you don't own the roads, and you don't own the property and lives you may destroy if you give a variable a stupid name or allocate some memory wrong.
My friends and I grew up doing all kinds of stupid things to our cars to make them go faster, one guy had a 5 psi turbo system pushing over 20 psi of boost because he broke the pressure sensing system. We did stupid, stupid things to our cars and generally ended up taking to them junkyard. It is a Very Good Thing it was prohibitively difficult for us to jumper in to the computer and start messing with stuff, because we would have. The more road blocks to people like us messing with their ECU's the better.
We (The US) already have laws that hold you accountable for being criminally negligent if you do a thing and cause harm to person or property. Do you really need additional protections from keeping yourself out of trouble? Is the only reason you don't do a thing is because you might be breaking the law?
We (The US) have laws that hold people accountable for trespassing and theft, but I'm guessing you still lock your doors.
A fundamental principle of engineering is protecting people from themselves, this is absolutely nothing new. Your life has been saved countless times because some engineer somewhere decided you didn't get to have a choice in something. (Maybe you like 50 ft falls, who are they to say that you should have to intentionally jump the handrail to hurt yourself?) It's Murphy's Law: if it's possible to do something stupid, somebody will and they might kill themselves and others in the process. So you make the stupid things hard to do.
In this case the stupid thing to do is messing with a computing system that handles multiple mechanical and electrical systems where a misnamed variable or some mismanaged memory could be extremely dangerous.
If you just have to tinker with something you can still buy/build a race car and take it to the track. Really, you should, it's fun.
My friends and I grew up doing all kinds of stupid things to our cars to make them go faster, one guy had a 5 psi turbo system pushing over 20 psi of boost because he broke the pressure sensing system. We did stupid, stupid things to our cars and generally ended up taking to them junkyard. It is a Very Good Thing it was prohibitively difficult for us to jumper in to the computer and start messing with stuff, because we would have. The more road blocks to people like us messing with their ECU's the better.