1. Infrastructure is used over time, though. Maybe you buy cars for cash but not everyone does. It's maybe a fair idea to pay a bit every year so that those who pay tax in that year pay for something being used in that year.
2. Sort of, but it's also a useful stat in that it tells us what % of our wealth we are paying on.
It's not about paying cash for cars. If you buy a car on a loan, pay it off before you get rid of that car. Don't just add that debt to the debt you incur for its replacement.
It may be a useful stat but it isn't an excuse to go farther in debt.