Cloud providers make sure that developers can easily scale their applications.
For example, we could have developed a social network application, but we can't be sure how many resources we need.
Mostly, we'll estimate based on the collected sample usage data, educated guesses, and so on.
During the fetching resources phase, we increase the required resources in case of high demand. Of course, increasing resources also increases the cost of owning an application.
The application's usage pattern will never be a flat line, so we never need the same number of resources. The resources needed will vary on a day-to-day, or even; hour-to-hour, basis.
Cloud providers make it easy to have only the required number of resources at that point in time.
This is very economic, and makes sense when we can't estimate the usage of a startup...
