Why do rings go bad???

I'm not the most mechanically inclined, but I have fuel in my oil and usually have to put a quart of oil in every week.. Tomorrow I am getting a compression test done to determine if the rings are bad, and if they are get them replaced. My question is what caused them to go bad? If I'm going to replace them obviously I need to replace or fix whatever made them bad to begin with, to prevent this from happening again... So again what would make them go bad? Anybody?