I mean yeah, but I want to buy a house soon. Me closing an account will have a negligible effect on the system but a large effect on my ability to get a mortgage.

The credit scoring alhorithms don't look at historic balances for credit cards, just current balance and available credit, status and age of the account. Having an account open for a long time that isn't currently late is a proxy for 'has paid bills consistently' even if it may not be accurate. If you regularly were really late, the algorithm assumes your account would have been closed.

Not using available credit proves you aren't an addict. Addicts eventually can't keep up with their bills.

Depends on what you mean by 'should be'. Are you talking about what it morally should be, or what it should be based on historical patterns?

I am guessing that data has shown people who utilize less of their available credit are more likely to not default. Whether that is morally better or not is up to you.

As for the reason this is the case, I am guessing it has to do with resisting temptation and not living right at the edge of your means. Having credit but not using it shows that you have a buffer between where you are and destitution.

You have credit available to you and you aren't maxing it out. You're exercised self control.

What you don't do with a credit line is just as important what you do with it.