I can think of a few reasons here but I think it comes down to boredom. Students are not only failing because they are not being challenged but because we have been stuck in the same educational mindset since the 50's! We need to update with the times and learn to teach kids and teens better, encourage them more so they are not bored and risk losing them completely to dropping out.
Why do you think this is such a big issue today?
There isn't just one reason why it happens but several reasons. The main ones come down to children having issues at home, learning issues such as ADHD that go diagnosed, and boredom. There are some teachers who do their best to make an impact on a child's life but not all children can be reach for one reason or another. School systems in poorer areas tend to be rundown and only able to hire teachers who don't care about education. Many of these schools end up closed down.
I would say it has to do with the students being bored as well as the teachers being underpaid. If I was a teacher and felt undervalued, I would work a whole let less on going the extra mile in my career. Teachers who earn more tend to go above and beyond for their students.
I did an online poll a few years ago and found that the students that were considering dropping our or already had, the primary reason was boredom. I think changes need to be made to ensure our students don't start sliding backwards. The more children we have dropping out, the more criminals will be on the streets.
They usually don't like the experience. As I mentioned in another thread one of my son's friends dropped out and it was down to not liking classroom learning. Too many distractions and not enough one on one teaching. He took up home schooling and is getting straight A's now.
I noticed it as a problem when I was still in school, today it is even worse. Schools are often overcrowded and under-educated. Several issues can results from this and one of them is kids giving up.