If I had kids, the family computer would be right smack in the middle of everything and the kids would not have their own computer.
Our kids had to use the computer in the family room. That way, nothing was hidden. They bought their own after they turned 18 and got their own jobs to pay for them.
Why didn't the parents check history to see what the kids were doing on the computer? Even if the kids deleted stuff, the parents could still pull the info out of the bin. It sounds like they weren't even checking.
We had one computer and it was in the dining room; monitored all the time. There was a time limit as well. They also knew I was computer savvy and put the fear of death into them that I could find anything I wanted on their computer:)