It's messed up because rent could be let's say $800 to $3,500 a month, if paying that every month on time isn't an indicator that you have consistent income to reduce risk on other loans then I don't know what is. It's especially messed up if the same system will ding your score if you buy $8 headphones and forget a payment.

Things are slowly being updated. And rent not being included is a pretty big error that needs fixing.

Last time I got a loan they asked me about my rent/mortgage (and utility!) payments so they could subtract that amount from my take-home pay when determining the risk of me defaulting on the loan. They seemed to assume I'd be paying my rent first and consistently regardless of any other debts I'd accrued.

I think that's a valid assumption. That's also why it's easier to get a mortgage on your primary house instead of an investment property.