Once upon a time (all the best stories start with "Once upon a time"), there was a computer manufacturer, let's call it by a totally random collection of letters, let's say "JCN".
JCN had a brand new computer that it was producing (called the QD-BU). One of the really cool things about this computer was that the hard disks on it were HUGE. Twice the capacity of any PC available at the time. This machine came with a 20 MEGABYTE hard disk!
Oh, and did I tell you it was FAST? It was so fast, you could move the heads around on the hard disk in only 10 milliseconds!
JCN was quite proud of their new computer, and they made sure that it was rigorously tested. They made sure that every component in the computer was of the highest quality, even the hard disks. It was especially important that the hard disks work well, because with all that disk space, people would store more and more data on the hard disk.
After months and months of testing, JCN decided that their computer was ready to fledge its wings and take flight. They launched it with MUCH fanfare, and it was very well received.
Unfortunately, they realized soon after the launch that there was a problem. Users started reporting that hard drives in the QD-BU were starting to act "badly". They would corrupt data seemingly at random. JCN was NOT happy at hearing this, after all, they had spent a lot of time and money ensuring that the QD-BU would be better than any other computer available.
The problem was that the manufacturer of the hard drives couldn't produce them in quantity. Their quality suffered when producing drives in quantity.
JCN worked to fix the problem with the manufacturer, and eventually everyone was happy.
Of course, JCN tried very hard to learn from the lessons of the QD-BU. And their key takeaway? Not that they needed to be careful about which vendor they chose to make their drives.
Instead the lesson they learned was "Fast hard drives break". So for their next generation of computers (the QT/3), the hard drives were much slower. They took 85 milliseconds to move the heads, but they were MUCH more reliable than the old QD-BU drives.
Of course this is only a bedtime story. It has no relationship to the real world whatsoever.