Specifically, printf is an oddball function because it uses the varargs mechanism, and the whole format strings mechanism is inherently risky because it effectively bypasses the type system and says "trust me." Back when I was learning C, on a Mac with THINK C, misusing printf was a sure-fire way to crash the computer very quickly, especially since misaligned accesses of 16-bit or 32-bit words caused crashes. Compilers now go to a great deal of trouble to try to do additional safety and consistency checks.
Don't get my wrong, I grew up using printf, and it is massively useful. But it was designed when computers were much smaller and simpler, and design tradeoffs were made back then that probably wouldn't be chosen today. So printf, along with a whole family of related functions, has been a seething mess of a security and safety hole longer than most programmers have been alive.