How do people become the way they are?

I'm a working cl guy in my mid twenties, I like working on cars, racing, drinking, smoking, chasing girls and on and on. I like intellectual stuff a lot less. But is there some deaper reason, why is it that when I talk I just say what I think and use a lot of profanity and other people think about every word they say. Is there a reason for all those kinds of traits or is it just random?