That's not because it measures your value as a consumer, though. It's because the the accuracy of their risk estimation is greater when there are more open accounts to analyze. (And even then, the relative "penalty" is small.)
why does an account have to be open to analyze it? Surely me successfully paying every monthly payment and having money to spare to pay off the loan early would indicate that my risk as a borrower is lower than someone who can barely make payments? If we were talking years down the line it should weigh less than an open account but my score dropped instantly after closing out the loan.
Maybe there is a regulatory aspect I don't understand that restricts analysis of closed accounts or something. Barring that Occam's razor would suggest that it hurts your credit score because paying off a loan early deprives the lender of interest which makes you a less appealing candidate at a given rate. After all, credit scores are a product for lenders, if it didn't do this they might go to another bureau that does.
Fundamentally the opacity of it all is a problem in its own right. We don't have any real insight into how the calculations are made but they dictate huge amounts of our lives.
How about when the only change to your credit profile is paying down multiple accounts, on time and seeing your available credit increase, your credit utilization decrease, your account aging increase...
