It's really important to take them at the same time everyday. That isn't always easy to remember.
Also it's a numbers thing. There are a lot of people on the Internet so think about it someone is going to be that 2%. So out of a hundred girls 2 are going to have had it happen just based on the infallibility of it not just the other reasons you mentioned. A thousand means 20 girls, ten thousand means 200 girls, and a hundred thousand means 2000 girls. Millions of people are on the Internet that is a lot of women falling in that 2%
The pill isn't the same as it was a decade ago, not to mention 20 years ago, it has come down a lot in the amount of hormones that it used to contain, less hormones means less complications. Many women don't know if they have a lot of breakthrough bleeding then it could be because the pill they are on doesn't have enough hormones to keep them from ovulating. Also the pill doesn't alway keep you from ovulating when working correctly, but instead doesn't allow a fertilized egg to implant. Most people aren't even aware of that.
And then there are the people who just aren't aware of how it works and how to take it. There is a question on here today from a girl who took 4 at once after she missed some pills... That is just crazy!