yep, and changing the oil on my motorcycle could cause scalding hot oil to burn me, but well documented processes from the vendor generally limit this risk. Repairing the power regulator for my refrigerator could have caused a shock, however repair manuals clearly instructed me to unplug and de-energize the appliance.
Tell me, grab a person off the street and ask them to say, replace the motherboard on your laptop.
That's it', you'll walk them though it, but you will not be allowed to comment on what they're doing. You'll demonstrate, they'll mimic. They are allowed to use anything they have.
Would you do it? Would you risk your computer? You can show them how to take it apart and provide all the replacement parts, they can watch you take it apart.
But they probably won't have the skill to. You tell them to use a #0 Phillips screwdriver, and they'll take their butter knife. Ask them to pry and they'll use a chisel.
If you're lucky, you'll just have a scratched up case. But more likely than not, they'll have screwed things up worse.
That's the real problem.
Would you let any driver on the road change the oil on your motorcycle? You know, perhaps the teenagers texting and pretty much oblivious to everyone else on teh road? And expect them to not get burned with hot oil?
The problem is most people are unskilled, and overestimate their skills. You tell them they can fix their phone? Chances are they'll wreck it even worse and make what was a simple $50 fix into not-economically-repairable.
It's why you have those idiotic "warranty void" stickers, moisture indicators, security screws, etc. These at least generally kept the unskilled from making things worse - if you were skilled enough to buy the right tools or brave enough to void warranty, chances are you at least had enough basic skills to not make things worse.
Warranty fraud is a big issue, and if you haven't seen someone lie straight up that it was not soaked in water despite a growing puddle of water on the counter underneath the device, you haven't seen anything. And yes, they'll demand a brand new unit replacement.