It can be hard to predict how your business will grow, or if and when you will require extra resources for short term 'bursts' of traffic or transaction volume. Increased growth or other demands often demands running applications with high load, or additional applications that most traditional hosting models cannot handle.
So it's a big advantage that Azure was built to scale alongside your business. One way Azure does this is by loading your applications as a cluster that allocates a web application to a specific set of processes. The result is that all of your applications are not forced to run off a single server and you will thus never run out of server capacity. As a bonus, Azure can even be managed to auto scale based on load or schedule.