Why learning to program alone is a terrible idea

well, i learned to program alone ;) Started with C#, then switched to HTML/CSS(/JS? i don't remember it anymore) and then in 10. grade learned Java. But i never finished a programming book! For me it just doesn't work that way. I started with some idea and tried to do it. First a simple guessing game (you had to guess the number and it would return whether you're above or below), a few websites, then a program to manage my homework which scheduled it to be as lazy as possible, taking into account free slots between classes. I still first have the idea and then try to implement it, learning by doing is what works for me (also applies to math. The lectures are important and so, but it falls and stands with the assignments you complete. Just don't try to do it alone).

When i was in school, programming was a hobby and not super important. I just did it irregular in the evening. But doing something with friends is more fun and programming is something that should not be done isolated, entire project fail because of that. Communication is key. I just did other things to learn how to work in a team.