There is this phenomena where novice programmers have a strong desire to always write their own code for everything, completely shunning third-party code libraries. They typically believe that their method is more secure, more controlled, and more productive. These novice programmers often graduate from this stage as they realize that code written by others is often better than what they can write themselves.
How do you describe novice programmers who want to build everything themselves?
I used to call it "DIY programming". I've also heard of the "Not invented here syndrome", but that seems to apply to institutions rather than novice individuals.