I think that works for ISPs because their service area and customer base are arbitrarily defined and within their control. They don't have to worry as much about a datacenter suddenly opening up in the middle of a neighborhood that throws off the profitability of everyone else.

And they can also impose things like bandwidth caps to curb some less-profitable customers' usage. But cloud providers, by design, are charging "per use" and expected to scale "indefinitely"... at least for expected use cases.