The ratio of avaialbe credit to credit used is an essential part of the scoring process.
The age average age of accounts is essential as well.
The number of revolving interest accounts (3 is the right number) is used too.
This means that when you close your oldest credit card you get dinged 3 ways... Which is why this game is not about helping understand who will default but more about understanding who will go into an ass-ton of debt, so much debt that they can barely manage the minimum payments.
A good credit score is a "I'm just stupid enough" to lend money to want to barrow money, but not so stupid I won't pay you back-score.
It's intended to opress the individual; create a super-ego whispering, in a deep sexy voice, "Oh, you would be sooo bad if you took out another loan" and an ID saying back "Oh really....". There doesn't need to be a grand conspiracy of hegemonic repression, it's simply the most profitable course of action.