I don't really care about percentages, either. But for some industries, the difference between "two 9s" and "five 9s" can be millions of dollars, so that's why they're published that way to the customer.

Except that customers lean so hard on those extra nines that they create processes where no work can be done when the service is down.

Less reliable products aren't allowed to become bottlenecks in the first place, at least at any B-tier or better businesses.