How about when that operation is at the core of your business logic and happens multiple time a day? How about when it's a blocking operation? There are plenty

How about when that operation is at the core of your business logic and happens multiple time a day? How about when it's a blocking operation? There are plenty of cases where your rule doesn't hold true, and I don't think that they're that uncommon. Plus having many machines has the advantage of a higher granularity of control over workload and balancing.