Why are the epistles so important?

Most of them were written by one person, a human, and some people regard every word as biblical law. The gospel came from Jesus and the Torah came from god to Moses (and all of jesus' teachings can be found in the Torah, with the two main commandments of love). so why does everybody take the letters like they're the bible itself? In my opinion, people should stop taking verses out of them, and take from the Torah and gospel instead.