The key benefits to using the Cloud compared to physical infrastructure are costs, scalability and time.
As an example, most businesses require, at a fundamental level, software, servers to authenticate users and control data access, storage servers to host the data and an IT Team to manage that infrastructure. These pieces of infrastructure age and need replacing every 3-4 years for performance reasons.
The IT Teams need to spend time managing this infrastructure and fixing it when it goes wrong. This is a considerable cost deficit to businesses and is usually the most significant spend by most annually. The Cloud removes this infrastructure and, as such, takes away a large chunk of the costs associated with it.