Many people, like you just don't get it.
You're 18 - you're excited to be a computer programmer. You find a local college that charges $10,000 a year. Very cheap by today's standards. You apply for student loans, and they cover you for 4 years. That's $40,000. Seems reasonable. You'll get a $75,000 job out of college, you imagine, as that is the average salary, and you'll be able to pay that off in no time.
That is usually what people think. But the reality is so far off than that.
You finish college - you can't get a computer programming job immediately. You can't afford paying the $200 monthly payment - so you defer your loans, while you work at Walmart. A year later, your loans are now up to $45,000 with interest.
You now get a first programming job, but it only pays $40,000. You find after moving out of your parent's house, and getting an apartment. The $250 monthly payment is a tight squeeze. So, you offer to pay $100 - they don't accept it. So, you defer your payments.
You can't find a higher paying job in your area - you decide to go to graduate school for 2 years. You get $20,000 more loans. Your loan is now up to $65,000 and increasing every day with interest.....
When you graduate from graduate school, after living with your parents for 2 years, not making much money (because you're in school), your loan is now up to $75,000 with a $350 monthly payment....
You still can't find a job for a few months, then get a $50,000 job. You pay the $350/month payment for a year, living on ramen noodles and squeezing pennies together, then your car breaks down, you can't afford to pay the $350... so you default and stop paying.
5 years later, your loan is now over $100,000 with interest. And the monthly payments are higher, all while you aren't getting paid much more.
This is how it usually happens.