> What you mention is basically to reduce the costs of counting, and is still usage-based metering, just with a reasonable guess to make payment more frequent.

That's not the motive where I live. There's basically 2 reasons: (1) customers (esp. those, often less well off, that resort to “money earned, money spent”) like the predictability of it; and (2) depending on the season spending changes significantly (heating, cooling), whereas salaries don't.

Usually the corrective amount is also paid out over a period of months if it exceeds X% of one month's spend.