- they are highly theoretical and biased against people who are not good at math; I studied CS, and I had to take more electrical engineering and math courses in my first two years than programming-related classes. This is very demotivating for someone who goes to university to learn programming, rather than physics or advanced mathematics
- they take too long and are full of useless classes (useless for getting a job, not in general)
- although the courses are free, it is very expensive to support yourself for the 3-4 years it takes to finish university, and you also need to buy books and other materials
- the most difficult courses are usually not programming related, but science; so you could invest 4 years of your life and end up without a diploma because you couldn't pass Advanced Physics or Calculus 3, despite being a good programmer.