What exactly is the purpose of a Patron Saint?

Question

From this question: How can a particular trade of modern times get a patron saint?, I learned that St. Isadore is the patron saint of computer programmers, a group of people in desparate need of a saint if there ever was one.

That said, as a Protestant, I'm not exactly sure what St. Isadore is supposed to be doing for computer programmers. I know that saints aren't worshipped, nor are they even prayed "to" in the sense that they would answer prayers with something magical - but what exactly is their function? I'm assuming that if the church is going to go through all the trouble of recognizing and naming a saint, there's gotta be a reason for it.

Answer 1

From http://www.catholic.org/saints/patron.php

Patron saints are chosen as special protectors or guardians over areas of life. These areas can include occupations, illnesses, churches, countries, causes -- anything that is important to us. The earliest records show that people and churches were named after apostles and martyrs as early as the fourth century.

The purpose of a Patron saint is two-fold.

• One purpose is that they are someone to use as a model - to pattern our behavior after them in a certain area of our life, or, as the article says, we can follow their example.

"I do also say it is well to keep before our eyes the supreme adventure of a virtue. If you are brave, think of the man who was braver than you. If you are kind, think of the man who was kinder than you. That is what was meant by having a patron saint."

– G.K. Chesterton (“The Supreme Adventure,” Utopia of Usurers)

• The other is that we can turn to them for intercessory prayer:

  Apparently, we can ask them to pray to God for us, which is an alien though to most protestants, but common among Eastern Orthodox, Oriental Orthodox, Roman Catholic, and Eastern Catholic practice.