Because they had no way of knowing that it was a "bad choice".
No different than buying a defective baby crib or car seat. You won't know that it was a "bad choice" until it's to late, unless someone tells you that it's a bad choice.
Not so much. With all the resources online you can learn just about anything with a little common sense and searching multiple sources. And these devices aren't defective when sold, they are doing exactly what they should under the given circumstances. What is defective is the operator's understanding of the device.
If these devices were failing because of manufacturing defects not known to the public I would agree completely but this is not the case.